# Intern Projects By Year

Past and Present Interns: Who they are, where they came from, and what they're doing.

## 2021 Interns

Aug 13 Symposium Program | AAS Abstracts

1. Moira Andrews (Purdue University)

ADVISOR: Dr. Rainer Weinberger (ITC; ITC Fellow)
MENTOR: Dr. Sirio Belli (OIR; Clay Fellow)

PROJECT TITLE: Were the first massive galaxies ellipticals or disks?

Abstract: Massive galaxies in the local universe are predominantly elliptical systems, in which stars follow randomly oriented orbits around the galaxy center. On the other hand, lower-mass galaxies appear as rotating disks, with all the stars lying on a well defined plane. This, however, does not need to be the case in the early universe, when the first massive galaxies were formed. Using TNG, which is one of the most advanced numerical simulations of galaxy evolution, the student will measure the degree of rotation in massive galaxies as a function of cosmic time. Recent observations suggest that massive galaxies form as rotating disks and then slowly become ellipticals by merging with other galaxies. The student will directly test this hypothesis by following simulated massive galaxies from their formation to the present day, and assessing whether the degree of rotation changes with time and if it is affected by galaxy mergers.
Skills: the student will need some familiarity with Python in order to be successful.

2. Olivia Aspegren (Yale University)

ADVISOR: Dr. Howard Smith (OIR)
MENTORS: Dr. Matthew Ashby (OIR, HEA)

PROJECT TITLE: Cosmic Rays, Colliding Galaxies, and Star Formation with SOFIA

ABSTRACT: Collisions between galaxies are ubiquitous, and drive massive bursts of star formation and the growth of supermassive black holes. Over cosmic time, these cataclysms help to build up the populations of stars and Active Galactic Nuclei (AGNs) seen today. During their most active phases these interactions light up the galaxies, turning them into ultra- or even hyper-luminous monsters that are detectable across billions of parsecs and deep into the cosmic past. In our work using the PACS instrument aboard the Herschel Space Observatory, we have discovered spectral evidence that one of the byproducts of massive star-formation is the production of dramatically enhanced cosmic rays which in turn ionize the gas, inducing crucial chemical and heating effects in it.

We have recently used SOFIA, the Stratospheric Observatory for Infrared Astronomy, to obtain far-information measurements to extend the small set of PACS observations to new galaxies, to determine if the dramatic and unexpected effects are common or rare. This REU internship will emphasize work with SOFIA/FIFI-LS spectral datasets of ultraluminous galaxies, but the intern will also gain familiarity with other space missions and with computational modeling. The student will work with our team to prepare one or more papers for publication about star formation and luminous galaxies. Other issues are likely to involve the role of AGN feedback to stimulate or suppress star formation and the existence of a previously underestimated (but massive) cold dust component. A final question is whether or not luminous galaxies in the early universe (whose morphologies are not known) follow the same star formation processes we find in the local universe.

3. Luis Gabriel Bariuan (Massachusetts Institute of Technology)

MENTOR: Dr. Aneta Sieminagowska (HEA)

PROJECT TITLE: Quasars in the Early Universe

Abstract: A quasar is an extremely luminous active galaxy that is powered by a supermassive black hole. These black holes possess accretion disks that can, in some instances, create large-scale jetted outflows. The connection between the accretion-outflow process is dictated by the formation and growth rates of the black hole, and this physical process may be studied via multiwavelength observations. The high luminosity of quasars also permits us to observe them in the early Universe, providing insight into quasar evolution as a function of Universe age.

In this project, the student will characterize the observational properties of the distant quasar population in the context of accretion and outflow. Spectral models will be developed, and physical properties of the quasars will be deduced from these models. This work will utilize data from radio, optical, UV, and X-ray observations. Results will additionally be compared against properties of nearby quasars to determine what differences, if any, are present as a function of Universe age.

Skills and Interest Required: Students should be interested in astrophysics and black holes. Concepts such as electro-magnetic radiation, statistics, data reduction methods, image and spectral analysis techniques will be covered with this research. Students interested in learning/developing computer programming skills preferred as research will utilize Python and telescope-specific software suites.

4. Victoria Catlett (University of Texas at Dallas)

ADVISOR: Dr. Andra Stroe (HEA/OIR; Clay Fellow)
MENTOR: Dr. Grant Tremblay (HEA)

PROJECT TITLE: What causes the dichotomy in the radio black hole population?

Abstract: The most massive galaxies in the Universe host an active black hole at their center. A significant fraction of these black holes shine bright at radio wavelengths, implying the presence of relativistic electrons spiraling through magnetic fields. The radio source population shows a clear dichotomy based on the morphology of their large scale radio emission. In Class I, the acceleration of electrons occurs close to the central black hole resulting in compact radio emission. Class II have powerful and relativistic jets traveling for hundreds of kiloparsecs, before terminating in bright hotspots. Understanding what causes this dichotomy between Class I and II galaxies is one of the biggest challenges in modern radio astronomy. We have identified the first secure hybrid morphology radio sources (HYMORS), where a mixture of the two Classes can be observed on either side of the host galaxy. The student will analyze recently completed Gemini optical spectroscopic observations of these HYMORS, taking charge of the unique opportunity they provide in studying differing morphologies resulting from a single central black hole engine. The student will yield key insights into what causes the Class I vs II dichotomy, helping resolve a question that has puzzled astronomers for almost 50 years. In the process, the student will learn about optical and radio astronomy concepts and gain experience with standard optical data reduction software. The student will also become familiar with concepts of galaxy formation, black hole physics, emission line physics and non-thermal phenomena.

Skills: the student should have some knowledge of the Linux operating system, and with scripting and programming in general. Some knowledge of Python in particular would be useful, but is not required.

5. Amanda Chavez (San Diego State University)

ADVISOR: Dr. Rafael Martinez Galarza (HEA)
MENTORS: Drs. Rosanne Di Stefano (HEA) and Vinay Kashyap (HEA)

PROJECT TITLE: Looking for high energy transients and transits in large X-ray datasets

Abstract: Existing astronomical X-ray catalogs offer an unprecedented opportunity for discovery. Several groundbreaking discoveries in high-energy, time-domain astrophysics, such as TDEs with quasi-periodic oscillations, or transients indicating the presence of the most massive black holes in the universe have been achieved somewhat serendipitously. But a careful and systematic examination of existing datasets from X-ray missions such as the Chandra X-ray Observatory and the XMM-Newton telescope are needed to further increase the discovery rate. In this REU project, the student will be working with experienced CXC astronomers to fully explore the variability aspects of the Chandra Source Catalog 2.0, both at short and long timescales, in order to detect unidentified transients that are scientifically compelling. This includes X-ray transits due to exoplanets, microlensing events, and fast X-ray transients. The student will employ data mining and anomaly detection methods in order to find these objects and will work on further characterizing them using their photometric, spectral, and variability properties, as obtained from the catalog. This project is an opportunity to learn about data-driven discovery in high energy astrophysics.

6. Jee-Ho Kim (University of Virginia)

ADVISOR: Dr. Sirio Belli (OIR, Clay Fellow)
MENTOR: Dr. Rainer Weinberger (ITC; ITC Fellow)

PROJECT TITLE: Stellar chemical abundances in the first massive galaxies

Abstract: Most elements are created in nuclear reactions within stars; however, not all elements are produced in the same way. For example, magnesium (Mg) is produced during the final explosion of short-lived massive stars, while iron (Fe) comes mainly from low-mass stars, which take billions of years to explode as supernovae. Therefore, measuring the abundance of Mg, Fe, and other elements allows us to estimate how long the process of galaxy formation lasted. The student will analyze the stellar chemical abundances in the TNG hydrodynamical cosmological simulation with the goal of making precise predictions for measurements to be made with the upcoming James Webb Space Telescope (JWST). The student's work will help guide the interpretation of the first JWST spectroscopic observations of massive galaxies at high redshift.
Skills: the student will need some familiarity with Python in order to be successful.

7. Amanda Malnati (Smith College)

ADVISOR: Dr. Dong-Woo Kim (HEA)
MENTORS: Drs. Rafael Martinez-Galarza and Francesca Civano (HEA)

PROJECT TITLE: Chandra Galaxy Catalog

Abstract: Using the Chandra observations for the last two decades, the Chandra Source Catalog version 2 (CSC2, released in 2019) provides 317,167 unique X-ray sources with accurate positions as well as high quality photometric, spectral and temporal properties. CSC2 is the major X-ray source catalog with the most precise source position and with the least confusion ever built in X-rays. In this program, we will utilize CSC2 to build a large (about 10,000), clean (with least confusion and contamination) X-ray selected galaxy catalog. To obtain multi-wavelength data, we will cross-match CSC2 with the following sky survey catalogs covering from IR to UV: SDSS, Legacy, DES, GAIA, PanSTARRS, WISE, 2MASS, and GALEX. We will classify X-ray sources and build the Chandra Galaxy Catalog (CGC). For the X-ray sources with optical spectral data, we rely on the spectroscopic classification, and we will further extract the galaxy properties (e.g., redshift, age, SFR, mass) from the spectral data. For X-ray sources with no spectroscopic observations, we will extract similar information (photometric redshift, age, SFR, mass) from the value-added catalogs for SDSS, Legacy, and DES. The primary classification schemes depend on the source extendedness, proper motion/parallax, and AGN strengths. Our preliminary results show that about 40K, 150K, and 100K of X-ray sources have counterparts from SDSS, WISE, and GAIA catalogs, respectively. We expect to find more than 10,000 galaxies with multiple counterparts from other catalogs. The preliminary sample of galaxies (identified by optical spectra) has the redshift ranging from 0 to 1.6 with z=0.3 plus or minus 0.2. We will further investigate focused galaxy sciences, which can be done only with a large, unbiased sample. They include the X-ray luminosity function of galaxies, X-ray scaling relations and unusual, but interesting types of galaxies (e.g., XBONGs, E+A galaxies). The student can be involved in (1) cross-matching CSC2 and other catalogs, (2) classifying matched sources to build Chandra Galaxy Catalog, or (3) to perform focused sciences.

8. Carissma McGee (Howard University)

ADVISOR: Dr. Ana Bonaca (TA, OIR)
MENTORS: TBD ()

PROJECT TITLE: A cosmic hit-and-run: Has a globular cluster impacted the GD-1 stellar stream?

ABSTRACT: The GD-1 stellar stream is a thin ribbon of stars that can serve as an antenna for gravitational perturbations. In 2018, Adrian Price-Whelan and I used the exquisite data from the Gaia satellite and found a significant gap in GD-1 -- an exciting signature of perturbation. Stream gaps are produced when a massive object collides with the stellar stream. Based on the location and the width of the gap, we can estimate when and where the impact happened. My models so far indicate that an impact of a globular cluster could have produced this gap, so the goal of this project is to determine whether any of the known globular clusters in the Milky Way is the culprit. This is mainly a theoretical project in which you will learn how to calculate orbits of objects in the Milky Way and estimate how close each of the globular clusters ever came to the GD-1 stream. If a globular cluster passed close to the GD-1 stream, that will be the first time we see a globular cluster impact another object. If no cluster came close to GD-1, that provides strong evidence that GD-1 was hit by an even more exotic object, such as a clump of dark matter or a black hole.

9. Liam Nolan (Arizona State University)

ADVISOR: Dr. Rosanne Di Stefano (HEA, TA)
MENTOR: TBD, depending on student choice of project

PROJECT TITLE: Are three stars better than two at creating Type Ia Supernovae?

ABSTRACT: Type Ia supernovae (SNeIa) are highly energetic explosions that have been used to establish the acceleration of the expansion of the Universe. In spite of the important results derived from them, we still do not have a good understanding of the astrophysical systems within which they occur. We know that SNeIa are exploding white dwarfs. In order to explode, a white dwarf must either merge with another white dwarf or else gain mass from a giant or main-sequence stellar companion. Most models are binary models.

This project will be one in which we explore newly-developed triple models. The scope can be tailored to the interests of the student.
One potential project of a theoretical nature is to study the flow of mass within triple systems.
Another would be to conduct three-body dynamical calculations to study the pre-mass transfer and post-mass-transfer evolution of possible progenitor systems.
A data-based project would be to apply a variety of methods, including machine-learning-based methods to the study of multiwavelength data, including data from OGLE, or the TESS and/or Gaia space missions, to discover evidence of the types of triple systems that are likely to be progenitors of Type Ia supernovae. An interesting feature of this work is that it also has applications to the gravitational mergers of neutron stars and black holes.

To effectively work on any of these projects, it would be helpful if the student had some prior experience with Python or another high-level programming language.

10. Anna Simpson (University of Michigan)

ADVISOR: Dr. Ryan Cloutier (SSP)
MENTOR: Dr. David Charbonneau (SSP, AST)

PROJECT TITLE: Measuring fundamental planet parameters of a multi-planet system discovered by the TESS mission

ABSTRACT: NASA's TESS mission has discovered a pair of planet candidates orbiting a nearby low mass star. These planet candidates have unique sizes and orbital separations indicating that their bulk compositions are likely distinct as well. The goals of this project are to measure the physical and orbital properties of these planets and to use those results to inform our understanding of how these types of planetary systems form. We are seeking an undergraduate student with an interest in exoplanets and in data analysis to analyze the available data that we have procured of this system in order to measure the planets' fundamental parameters.

The successful applicant will have a basic working knowledge of computer programming. Experience with python or other similar scripting languages is an asset.

11. Noah Thompson (Whitworth University)

ADVISOR: Dr. Rachel Cochrane (ITC, TA)
MENTOR: Dr. Rebecca Nevin (HEA)

PROJECT TITLE: A multi-wavelength study of the dustiest, most highly star-forming galaxies in the early Universe

Abstract: Sub-millimeter detected galaxies represent some of the most intensely star-forming galaxies in the early Universe. Emission at these wavelengths originates from dust grains, which are heated by the UV emission from young, massive stars and then re-emit at longer wavelengths. These galaxies have large amounts of dust, and some emit little in wavelengths other than the far-infrared/sub-millimeter, and have been called optically-faint' or optically-invisible'. Others display curious morphologies at short wavelengths, which trace light escaping only from the least dusty regions of the galaxy.

In this project, we will study the multi-wavelength emission from a sample of ~700 sub-millimeter galaxies within the UKIDSS/UDS field (ref 1; see below). In particular, we will investigate spatial offsets between the emission detected at different wavelengths (ref 2), and how the incidence of such offsets depends on the properties of the host galaxy such as dust mass, star formation rate and geometry. A statistical investigation will be enabled by our large parent sample of sub-millimeter detected galaxies. We will also characterise the role of offsets in driving scatter in scaling relations, such as the IRX-beta relation (ref 3). Extensions to the project could include using simulations to disentangle two physical scenarios: individual galaxies with offsets that appear as multiple components, and merging galaxy systems.

The specific emphasis of the project will be set by mutual agreement between the student and advisors. Ideally, the project would lead to a short project report summarising the work, and later to authorship/co-authorship on one or more published papers.

The papers referred to above can be found
1. here ,
2. here (see Fig. 5), and
3. here (see Fig. 7). The IRX-beta relation describes the correlation between the excess infrared luminosity (relative to the UV luminosity) and the UV spectral slope.

Skills required: basic programming skills are preferred, but can be learned on the job.

12. Thomas Waters (University of Washington)

ADVISOR: Dr. Razieh Emami Meibody (TA)
MENTORS: Drs. Lars Hernquist (TA), Sirio Belli (OIR, Clay Fellow)

Dr. Meibody is offering a choice of two possible projects this summer:

PROJECT TITLE 1 of 2: Probing the impact of metallicity and the initial mass function on the rate of the inspiral and tidal disruption rate in stellar clusters around SMBHs
Abstract 1 of 2:
Develop techniques to study a variety of different star clusters around super massive black holes (SMBH) which are located at the center of different galaxies such as Milky Way. The goal would be to study the impact of the metallicity and thus the initial mass function of stellar mass black holes on the rate of EMRI as well as the tidal disruption rate. We can use some of the hybrid tools that we have been developing recently which connect stars with different metallicities to different BH populations and use them in some simulations of stellar cluster. This setup can be then put in some post processing codes and compute the rate of the inspiral for the BHs at different environments. For each of these environments we may use the most recent observational data for the density profile of stars and compute the signal etc. Some environments such as post star burst galaxies may give us larger signals and this is very timely to estimate how may this be related to the properties of the PSB galaxies.

PROJECT TITLE 2 of 2: Probing the radial dependence of the velocity anisotropy for Milky Way galaxies using the TNG50 simulation, and comparison with observations
Abstract 2 of 2:
One of the most important observables of the stellar halo in galaxies is the radial profile of the velocity anisotropy, beta. This parameter characterizes the extend to which stars are in the radial, prograde and retrograde orbits and can give us novel information about the assembly history of galaxies. Thanks to the recent observations, we have some knowledge about the beta. Here we aim to use the state of the art simulations of the TNG to compute the radial profile of the velocity anisotropy for a sample of MW like galaxies and compare them with observations.

Student skills required: the student undertaking this project should be familiar with Python.

## 2020 Interns

Aug 13 Symposium Program | AAS Abstracts

1. Samantha Garza (University of Dallas)

ADVISOR: Dr. Matthew Ashby (OIR)
MENTORS: Drs. Glen Petitpas (R&G) and Maria Jesus Jimenez Donaire (Observatorio Astronomico Nacional, Madrid, Spain)

PROJECT TITLE: GMC Dust Masses and Dust/Gas Ratios in the Whirlpool Galaxy

Abstract: The nearby grand-design spiral galaxy Messier 51, by virtue of its proximity and favorable inclination, affords a unique view into the processes governing star formation, and the student who takes on this project will use our existing data to tackle a long-standing problem: the relatively poorly-constrained dust-to-gas ratio in the ISM of galaxies.

Because it's so bright, the entire M51 disk has been mapped by infrared observatories including Spitzer, Herschel, and the JCMT with sufficient resolution to isolate individual Giant Molecular Clouds (GMCs) at multiple wavelengths extending out into the mm regime. Taken as a group, these observations will allow reliable estimates of total dust masses and temperatures for numerous GMCs. M51 has also been mapped in the low-lying lines of CO (J=1-0 and 2-1), which will provide an estimate of the GMC's gas masses.

The goal is to combine the available ground- and space-based broadband imaging with the CO spectroscopy to measure the dust-to-gas ratio for GMCs throughout M51. This will test whether the conventional estimates for the ratio (0.01) are valid, constrain how the ratio varies with GMC mass, star formation rate, dust temperature, galactocentric radius, and other measurables, and finally, provide by-GMC estimates of the star formation rate in M51.

2. Megan Gialluca (Northern Arizona University)

ADVISOR: Dr. Ana Bonaca (TA, OIR)
MENTOR: Dr. Sownak Bose (TA)

PROJECT TITLE: Is the dark matter fuzzy? Measuring the velocity dispersion in the GD-1 stellar stream

Abstract: Dark matter makes up 85% of the matter in the universe, but it is extremely hard to study because it is invisible -- it only interacts with the matter that we see through gravity. There are several competing models of dark matter, including fuzzy dark matter. In this model, dark matter is a particle of a very low mass (10^30 times less massive than the proton). This mass is so low that quantum fluctuations happen on astronomical scales, and result in a turbulent distribution of dark matter.

The GD-1 stellar stream is a collection of stars that used to live in a globular cluster, but have all been pulled out by the Milky Way's tidal forces and now travel around the Milky Way as a thin ribbon. The GD-1 stream is very narrow, which makes it an excellent gravitational antenna. In particular, the velocity dispersion of stars in the stream is an indicator of how "fuzzy" the dark matter is. Theoretical models predict that the amount of turbulence increases with the decrease in the mass of a fuzzy dark matter particle. A stellar stream orbiting in more turbulent dark matter gets heated, and its velocity dispersion increases. In this project, you will use measurements of stellar radial velocity in the GD-1 stream obtained with a high-resolution spectroscope Hectochelle on MMT to measure its velocity dispersion, and directly constrain the mass of a fuzzy dark matter particle.

Note: this project has been submitted for publication as Velocity Dispersion of the GD-1 Stellar Stream, by Gialluca, Naidu, and Bonaca (2020).

3. Noah Goldman (UMass Amherst)

ADVISOR: Dr. Nimesh Patel (SMA, R&G)
MENTOR: Dr. T. K. Sridharan (SMA, R&G)

PROJECT TITLE: Imaging Cold Dust around Wolf-Rayet Stars

Abstract: Mass-losing cool envelopes of Asymptotic Giant Branch (AGB) stars are a dominant source of dust grains and gas enrichment in the interstellar medium. Massive evolved stars in the Wolf-Rayet (WR) phase and as supernovae, each contribute much less dust to the ISM. Despite being relatively weak sources of dust, understanding the process of dust creation in WR stars is very important because these stars are likely to be a significant source of dust in the early universe (z>6; <1 Gyr age), due to the need for fast dust production (Gall et al. 2011). The physics of dust creation remains poorly understood in general, but particularly mysterious in massive evolved stars such as WRs. Usov (1991) suggested that in a WR + OB binary system, the stellar winds from both the stars would collide and form a shock front. In this wind-collision region, the gas may cool and compress very strongly, allowing the possibility of dust formation. Radio interferometers such as the Submillimeter Array (SMA) and the Atacama Large Millimeter/Submillimeter Array (ALMA) provide a great opportunity to directly image cooler dust around WR stars. We have obtained 345 GHz observations with the SMA towards two WR stars, WR 140 and WR 146, in 2012.

The student will analyze these SMA data, producing continuum images and flux measurements, and also study other available continuum data at longer wavelengths either from literature, or archival data, to study the spectral energy distribution. The data analysis will be done using the SMA data reduction software as described on the SMA observer center (using IDL routines, and the ALMA CASA software for imaging). No prior experience in these software is required, but a familiarity with Linux computing environment, and Python would be useful.

4. Mary Jimenez (George Mason University)

ADVISOR: Dr. Howard Smith (OIR)
MENTOR: Dr. Matthew Ashby (OIR)

PROJECT TITLE: Colliding Galaxies, Star Formation, and Black Holes with SOFIA

Abstract: Collisions between galaxies are ubiquitous, and drive massive bursts of star formation and the growth of supermassive black holes / active galactic nuclei (AGN). Over cosmic time, these cataclysms help to build up the populations of stars and AGN seen today, and during their most active phases they light up the galaxies, turning them into ultra- or even hyper luminous monsters that are detectable across billions of parsecs and deep into the cosmic past, into the so-called Bright Era era of cosmic star formation at z~3 only a few billion years after the big bang.

In an ongoing project we have compiled the largest, most reliable, and most complete spectral energy distributions (SED) of hundreds of mergers and luminous galaxies using newly reprocessed photometry from a dozen pioneering space missions and ground programs extending from the ultraviolet to the far infrared (about 33 wavelength bands). Using sophisticated new modeling codes, we have extracted from these SEDs dozens of key physical parameters from star formation rates, AGN luminosities , dust temperature, stellar mass, to the dustmass and character; we also have complimentary spectroscopic datasets. This unique sample has enough objects to offer excellent statistical analyses, we believe for the first time. The results so far have found important trends - including for example (1) the star formation rate versus the AGN luminosity contirbution, and (2) the mass of the supermassive black hole mass versus the stellar mass of the system. Results have also identified outlier objects whose behaviors offer clues to the inner physicalprocesses at work. All these new results are nearly ready for publication.

This past year, for the first time, we have used SOFIA, the Stratospheric Observatory for Infrared Astronomy, to obtain far-information spectroscopic and continuum SED measurements. Also, we have both new dust modeling tools, and extensive computational simulations of merging galaxies that can be used to test the modeling. Key issues include the role of AGN feedback to stimulate or to suppress ("quench") star formation, the nature of the ionized interstellar medium, and the existence of a previously underestimated (but massive) cold dust component. The spectroscopic data reveal underlying massive outflows of gas from galaxies, and a previously unreported powerful cosmic-ray component. A key question is whether or not luminous galaxies in the early universe (whose morphology is not known) follow the same star formation processes we find in the local universe.

This REU internship will emphasize work in all these areas, and the student will play a leading role in the data analysis and modeling, possibly including some some software development opportunities. Emphasis is on the new SOFIA datasets, but the intern will gain familiarity with multiple missions datasets, and with computational modeling. The student will be a part of our team, and will co-author and/or lead one or more papers for publication about black holes, star formation, gas outflows, and luminous galaxies. Some emphasis will be given to improving the SED modeling with new modules to enable more accurate retrieval of key physics.

5. Abigail Mintz (Yale University)

ADVISOR: Dr. Joseph L. Hora (OIR)

PROJECT TITLE: Investigating Massive Star Formation in the Cep OB4 Association

Abstract: The presence and formation of massive stars have major impacts on galactic structure and evolution, but the important mechanisms that control this process are still not well understood (e.g., see reviews by Zinnecker & Yorke 2007, Motte et al. 2017). Winds, ionizing flux, and outflows from massive stars and supernovae will affect the structure and inject turbulence in molecular clouds. Massive O and B stars typically form in loosely organized groups called OB associations, which also contain many low mass stars. It is likely that most stars in the Galaxy originated from OB associations, so determining the processes at work in these regions is critical to the understanding of star formation.
We have recently completed the first Spitzer/IRAC deep study of one of the closest OB associations, Cepheus OB4 (Cep OB4), in order to have the best sensitivity and spatial resolution on the environments of massive stars and to identify its population of lower mass young stars. Cep OB4 is a ~2 Myr old association at a distance of ~800 pc, and is an ideal region for comparison to star formation models for several reasons. It is offset from the densest part of the Galactic plane and relatively nearby, enabling us to resolve individual objects at a scale of ~1400 AU and detect young stellar objects (YSOs) down to a few tenths of a solar mass. Also, the region has a simple geometry, with the OB stars and H II region surrounded by a roughly circular molecular and dusty cloud into which the bubble is expanding, providing a testbed for sequential star formation models. The summer project will involve reducing and analyzing the IRAC data, along with existing near-IR and other available datasets from the WISE and Herschel infrared space missions, to identify YSOs and young clusters and test models of star formation.

6. Alexa Morales (Florida International University)

ADVISOR: Dr. Charlotte Mason (OIR, HST Fellow, CfA Fellow)
PROJECT TITLE: Measuring the timeline of cosmic reionization

Abstract: We cannot see the first galaxies which formed in the universe, but we can observe the impact they had on their surroundings. In the universe's first billion years the majority of hydrogen transitioned from neutral to ionized. This process, Reionization', was probably caused by photons from the first galaxies, and is an exciting frontier of observational and theoretical astrophysics. The Hubble Space Telescope and biggest telescopes on the ground can observe galaxies at the end of Reionization. By studying these galaxies and how they are affected by Reionization we can learn how Reionization started and about the nature of the very first galaxies. This project combines theoretical modeling and analysis of observations. The student will use existing theoretical models of galaxy evolution and large scale simulations of Reionization. The student will update the models using Python code to predict the evolution of galaxy properties (specifically, the Lyman alpha luminosity function) as the universe reionizes,using a combination of analytical and statistical techniques. The student will compare their model with existing observations of galaxies to measure the timeline of Reionization. These results will be be pivotal in understanding how Reionization took place, and thus the properties of the first galaxies.

Note: this project has been submitted for publication as The Evolution of the Lyman-Alpha Luminosity Function During Reionization, by Morales, Mason, Bruton, et al., 2021.

7. Jacqueline Patterson (University of Indiana)

ADVISOR: Dr. Kelvin Lee (R&G)
MENTORS: Drs. Andrew Burkhardt (R&G) and Mike McCarthy (AMP)

PROJECT TITLE: Developing Automated Workflows in Astronomical and Laboratory Spectral Data

Abstract: The influx of high-bandwidth, complex radio spectra generated by radio interferometers such as ALMA and the SMA, particularly as towards lines of sight that have complicated kinematics and chemistry like star forming regions, protoplanetary nebulae, and circumstellar shells, presents both a boon and a problem for modern astrochemistry. These spectra typically contain hundreds to thousands of molecular features, but we don't know what molecules many of these features correspond to: this is something we need to know, as molecules act as sensitive physical probes in these regions. Traditional spectroscopic analysis involving weeks and months of expert analysis cannot match the cadence of these experiments-fortunately, we have also seen a substantial increase in the sophistication of our computational capacity and algorithms, thanks to the heavy investment in open-source deep learning and data science tools. In this project, a student will learn basic data science skills applied to helping develop automated analysis workflows for rotational spectroscopy, with an emphasis on reproducibility and open-source development in notebook environments and Python.

8. Morgan Saidel (University of New Hampshire)

ADVISOR: Dr. Huiqun Wang (AMP)
PROJECT TITLE: Development Histories of Mars Dust Storms

Abstract: Dust storms are highly important for the weather and climate of Mars. They can grow to immense sizes that cover a large longitudinal channel, latitudinal band, or the whole planet. Large dust storms profoundly influence the visibility, thermal structure and atmospheric circulation of the Martian atmosphere and are of particular concern for spacecraft missions. The mechanisms through which large dust storms develop is at the forefront of current research.

The daily global monitoring by the Mars Global Surveyor (MGS; active mapping operations from 1999 to 2008) and Mars Reconaissance Orbiter (MRO; still actively collecting data) spacecraft for the past Mars decade provides a great opportunity to investigate the detailed development histories of large dust storms, which contain key information on the grown and decay mechanisms. Each large dust storm results from one or more dust storm sequences, and each dust storm sequence involves many dust storm members. Using MGS and MRO imaging and optical depth data, this project will examine how dust storm members grow, interact, and decay along the trajectories of large dust storms. The student will have the opportunity to perform data analysis using spacecraft observations and to contribute to the understanding of the Martian dust cycle which is fundamental to the Marian atmosphere.

The student involved in this project will makes extensive use of IDL so some prior knowledge of IDL would be helpful but is not essential. The ability to write and understand programs at a basic level is required.

9. Jafr-Tayar Shabazz (Florida International University)

ADVISOR: Dr. Yvette Cendes (OIR)
MENTOR: Dr. Edo Berger (OIR)

PROJECT TITLE: Searching for Transient Radio Signals in the Very Large Array Sky Survey

Abstract: Transient radio astronomy is the search for emission from exotic phenomena such as supernovae, neutron star mergers, flaring stars, and tidal disruption events. However, the field is limited by a lack of robust tools to sort through and find such transients, and large data sets at sufficient sensitivity for identification. In this project, the student will use data from the Very Large Array Sky Survey (VLASS) - the first all-sky survey with the VLA in over two decades - to develop tools for radio astronomers interested in radio transients. The student will then apply the developed tools to VLASS survey data to discover transient radio signals.

10. Vivek Vankayalapati (University of Utah)

ADVISOR: Dr. Andrew Burkhardt (R&G)
MENTORS: Drs. Kelvin Lee (R&G) and Mike McCarthy (AMP)

PROJECT TITLE: Constraining and Detecting New 13C-Chemistry for the GOTHAM Survey

Abstract: Carbon chains form the backbones of many of the most important and complex molecules in the universe, from complex prebiotic molecules to the ubiquitous polycyclic aromatic hydrocarbons to the carbonaceous material that forms dust and eventually planets. One way to constrain the formation mechanisms for carbon chain molecules is to study the relative abundances of the isotope-substituted counterparts, known as isotopologues and isotopomers. The ongoing survey GOTHAM (GBT Observations of TMC-1: Hunting Aromatic Molecules) is performing an extremely deep spectral survey of TMC-1, a cold, dark cloud in Taurus known for its exceptionally rich carbon-chain chemistry, with the larger goals of detecting and understanding the formation of aromatic molecules in the interstellar medium. In particular, these observations will facilitate the detection of many new isotopologues of carbon as part of the GBT Large Project. During the course of the summer internship, two students will collaborate on a two-part project to develop a theoretical and laboratory foundation to study the 13C-isotopologues as part of this survey. Both students will have opportunities to receive instruction on both components, depending on interest.

The student will begin adapting an existing chemical model to include the simulation of 13C-substituted species. This will include expanding the existing network for the new isotopologues, reducing the network's molecular complexity for computational efficiency, determining the significant methods of 13C enhancement/destruction, and determining relative reactivities among isotopomers. As the student develops their knowledge of the model, they will communicate the key species that require additional experimental follow up.

11. Leah Zuckerman (Brown University)

ADVISOR: Dr. Sirio Belli (OIR; Clay Fellow)
MENTORS: Drs. Sandro Tacchella (OIR; CfA Fellow) and Joel Leja (OIR; NSF Fellow)

PROJECT TITLE: What drives the evolution of galaxy colors?

Abstract: Galaxy colors are good indicators of the age of the stars they contain: blue galaxies consist of young, hot stars, while red galaxies are made of old stars that are relatively cold. At some point, blue galaxies undergo a poorly-understood "quenching" process and cease forming stars altogether; the mechanism by which this happens is one of the most important open questions in the field. By analyzing the colors of large samples of galaxies observed at different distances (and correspondingly different cosmic epochs), it is possible to study the evolution of galaxy colors throughout the history of the universe. At early cosmic times, when the universe was still young, most galaxies were blue and actively star-forming, while at late times most galaxies have become old and red. The rate at which galaxies change their color can be used to investigate the physical process that turns off star formation. The student will construct a simple empirical model for the evolution of galaxy colors with time, and compare it to observations from large, state-of-the-art galaxy surveys spanning a range of cosmic epochs. This comparison will yield new constraints on the physical processes that turn off star formation in galaxies.

## 2019 Interns

#### 1. Jea Adams (Amherst College)

ADVISOR: Dr. Nimesh Patel (R&G)
MENTOR: Dr. Quizhou Zhang (R&G)

PROJECT TITLE: Triggered star-formation in the globules of IC 1396

Abstract: The bright-rimmed globules at interfaces of ionized hydrogen (HII regions) and dense molecular clouds have long been studied as potential sites of star-formation. These edges are compressed to densities high enough to trigger star formation, due to shock fronts caused by UV radiation from the OB stars in the HII region. But direct evidence of this triggering effect on star-formation is difficult to establish observationally, and obtaining a fuller understanding is challenging because it requires observations at multiple wavelengths, on large angular scales, and which also have the high angular resolution characteristic of molecular line emission from high density tracers, as well as continuum emission from dust. We have recently published our results on a newly discovered protostar using Herschel and IRAM 30m observations of the IC 1396 globule A. (Sicilia-Aguilar et al., 2019, A&A 622,A118). We have also obtained SMA observations of this protostar, as well as another new source in the same globule. In this project, we will analyze the dust continuum emission in this source, and CO 2-1 emission from the bipolar outflow, to further improve our understanding of the phenomenon of triggered star-formation.

#### 2. Amanda Ash (University of North Georgia)

ADVISOR: Dr. Stephanie Douglas (SSP; NSF Fellow)
MENTOR: Amber Medina (SSP)

PROJECT TITLE: Magnetic activity variability in the Praesepe open cluster

Abstract: Stellar rotation and magnetic activity operate in a feedback loop where a rotationally powered dynamo produces magnetic fields, and then stellar winds carry mass and angular momentum away, slowing the star and weakening the dynamo. To measure rotation, we look for periodic brightening and dimming caused by starspots rotating into and out of view. To trace the magnetic field, we use indirect measurements like H-alpha and X-ray emission. Most surveys that compare rotation and activity don't account for potential activity variability, however, even though it's been shown that a single star's H-alpha measurement can vary significantly. Last winter, I carried out a survey of stars in the Praesepe cluster (M44) that tracked H-alpha simultaneously with photometric variability, in an attempt to correlate H-alpha active regions with starspots. The student will measure H-alpha emission from reduced MDM data and correlate H-alpha time-series with light curves from K2.

3. Zoe de Beurs (University of Texas at Austin)

ADVISOR: Dr. Saeqa (Saku) Vrtilek (HEA)
MENTOR: Dr. Nazma Islam (HEA)

PROJECT TITLE: Revealing the Structure of Sco X-1, the Brightest Source in the X-ray Sky (except the Sun)

Abstract: The student will reduce and analyze Doppler tomography observations of binary system Sco X-1 taken with the Magellan 6.5 m telescope in 2019 May. Specifically, the student will construct Doppler tomograms (a diagnostic technique similar to medical CAT scans) to image the structure of this system. The student will learn about optical telescopes, and about how these unusual data are obtained, reduced, and interpreted to understand the physics of this binary system. It is expected that the work will result in co-authorship of a refereed publication.

#### 4. Frederick Dauphin (Carnegie Mellon University)

MENTOR: Dr. Edo Berger (OIR)

PROJECT TITLE: Selecting Superluminous Supernovae from Transient Surveys with Machine Learning

Abstract: Superluminous supernovae are a rare type of stellar explosion whose power source is poorly understood. In order to characterize the observational properties of the class and compare them to models, we need to significantly increase the sample size of well observed events. Today's transient surveys (e.g., the Zwicky Transient Facility) produce hundreds of supernova candidates per night, but only a small fraction of these can be classified spectroscopically. This means we need a way to predict which candidates will be superluminous supernovae based only on information available at discovery: how bright they are and where they happened in the sky. Previous work has shown that superluminous supernovae preferentially occur in dwarf galaxies, whereas other types of supernovae are more likely to be found in more massive galaxies. Although the correlation is not perfect, this type of contextual information can be used to sift through the stream of transient discoveries to produce a much smaller sample of events for spectroscopic classification that are highly likely to be superluminous supernovae. We propose to use supervised machine learning to carry out this filtering, which most astronomers currently do by hand. The intern would explore various machine learning algorithms and train them on the set of all previously classified supernovae. The resulting classifier would then be used on new discoveries to determine which candidates we should observe spectroscopically. If this method is more efficient than human filtering, it will have wide-reaching implications for the Large Synoptic Survey Telescope, which will discover transients at an even more unmanageable rate.

5. John Della Costa (University of Florida)

ADVISOR: Dr. Howard Smith (OIR)
MENTOR: Dr. Matthew Ashby (OIR)

PROJECT TITLE: Colliding Galaxies, Star Formation, and Black Holes

Abstract: Collisions between galaxies are ubiquitous, and drive massive bursts of star formation and the growth of supermassive black holes / active nuclei (AGN). Over cosmic time, these cataclysms help to build up the populations of stars and AGN seen today, and during their most active phases they light up the galaxies, turning them in to ultra- or even hyper luminous monsters that are detectable across billions of parsecs and deep into the cosmic past.

We have a ongoing project that has compiled the largest, most reliable, and most complete spectral energy distributions (SED) of hundreds of mergers and luminous galaxies using newly reprocessed photometry from space missions and ground programs extending the ultraviolet to the far infrared (about 33 wavelength bands). Using new modeling codes, we have extracted from these SEDs dozens of key physical parameters from star formation rates, AGN fraction, dust temperature, stellar mass, to the dust mass and character; we also have complimentary spectroscopic datasets. This unique sample has enough objects to offer excellent statistical analyses, we believe for the first time. The results so far have spotted important trends - including for example (1) the star formation rate versus the AGN fraction, and
(2) the mass of the supermassive black hole mass versus the stellar mass of the system.
Results have also identified outlier objects whose behaviors offer clues to the inner physical processes at work.

Significantly, we have extensive computational simulations of merging galaxies that can be used to test the modeling. First comparisons confirm the reliability of the modeling codes, but much more remains to be done. Key issues include the role of AGN feedback to stimulate or suppress star formation, the nature of the ionized interstellar medium, and the existence of a previously underestimated (but massive) cold dust component. Another key question is whether or not luminous galaxies in the early universe (whose morphology is not known) follow the same star formation processes we find in the local universe. This REU internship will emphasize work in all these areas. The intern will simultaneously gain familiarity with multiple datasets and with computational modeling. The student will work with our team to prepare one or more papers for publication about black holes, star formation, and luminous galaxies. Some emphasis will be given to improving the SED modeling with modules to enable more accurate retrieval of key physics.

#### 6. Hannah Gulick (University of Iowa)

ADVISOR: Dr. Sarah Sadavoy (R&G; Hubble Fellow)
MENTOR: Dr. Luca Matra (R&G)

PROJECT TITLE: ALMA Observations of Protostellar Disks

Abstract: Planets form in dense, flat disks around young stars. The seeds for planet formation are small particles of dust within these disks that must grow from micron sizes to pebbles and boulders. The timescales for this formation process are not well understood, and recent theoretical models suggest that a good metric to study the onset of dust grain growth is through polarized scattering. This project will explore why some disks around young stars show evidence of polarized dust scattering (and hence grain growth) whereas other disks do not show this detection. One explanation could be that the masses and densities of these disks are too low for substantial dust grain growth at early stages. Another explanation could be that the undetected disks have poor geometry to detect dust scattering. Either explanation is critical to use this new technique to study how disks form planets at early (< 1 Myr) stages. For this project, the student will use observations of disks from an unbiased survey with the ALMA interferometer. The student will measure the mass, size, density, and inclination of these disks using a simple radiative transfer code to determine if the disk properties or disk geometry affects the detection rate of dust scattering.

#### 7. Caleb Harada (University of Maryland, College Park)

ADVISOR: Dr. Antonijia Oklopcic (TA)
MENTOR: TBD

PROJECT TITLE: Atmospheric escape in exoplanets

Abstract: A significant fraction of exoplanets discovered to date orbit their host stars at much closer separations than any of the Solar System planets. These close-in exoplanets are subject to intense stellar radiation, which can have dramatic effects on their atmospheres. The upper layers of a planetary atmosphere can get heated by stellar X-ray and UV radiation to temperatures of several thousand degrees, creating pressure gradients that drive a supersonic planetary outflow. Recently, the helium line at 1083 nm has been identified as an excellent probe of extended exoplanet atmospheres which contain evidence of atmospheric escape. The goal of this theoretical project is to establish what information about the uppermost layers of planetary atmospheres can be extracted from observations, particularly from transit light curves in the helium line at 1083 nm. The student will use a set of pre-generated models of escaping exoplanet atmospheres to produce synthetic transit light curves and investigate how the shape of the transit light curve depends on various properties of the planet and/or its host star.

8. Maryam Hussaini (University of Texas at Austin)

ADVISOR: Dr. Andra Stroe (OIR; Clay Fellow)

PROJECT TITLE: Unraveling the physics of shock cluster galaxies
MENTOR: Dr. Grant Tremblay (HEAD)

Abstract: Nearby clusters usually contain many old galaxies, with characteristic red colors indicating they stopped forming new stars long ago. Unlike peaceful nearby clusters, distant galaxy clusters undergo frequent cosmic collisions with other clusters. These collisions were commonplace in the early Universe, but astronomers recently realized they are just as prevalent in the nearby Universe. Studying far away galaxy clusters is difficult, but we can use nearby colliding clusters as probes of the early Universe. Cluster collisions drive dangerous cosmic weather': giant shock waves and turbulence which travel through galaxies like enormous tsunamis and tornadoes. As the shock passes through them, the typical old, dormant cluster galaxies can actually be awoken to start forming new stars. Capitalizing on unique optical data from the Gemini telescope in Hawaii, the student will be the first to unveil the spatially resolved physics of 'shocked' cluster galaxies. The student will measure the star-formation rate, the presence of black hole activity and the nature and strength of the ionizing radiation and how these vary within the galaxies. The student will learn how to reduce and analyze integral-field unit spectroscopic data and will become familiar with concepts of cluster formation, galaxy evolution, star formation and emission line physics.

For either project led by Dr. Stroe, the student should have some knowledge of the Linux operating system, and with scripting and programming in general. Some knowledge of Python in particular would be useful but is not required.

#### 9. Kenneth Lin (Univ. of Massachusetts Amherst)

ADVISOR: Dr. Dong-Woo Kim (HEA)
MENTORS: Drs. Nazma Islam (HEA) and Ewan O'Sullivan (HEA)

PROJECT TITLE: The X-Ray Galaxy Atlas

Abstract: Over the past 20 years, X-ray observations have changed our understanding of the galaxy population by allowing us to study in depth their high energy content. In particular, we are here interested in the hot interstellar medium, which is the dominant gas phase in galaxies otherwise lacking a significant gaseous component. This has a large impact in our understanding of their properties (e.g. total mass) and of their formation and evolution, hence on the history of the Universe. For this reason, we have built an X-ray Galaxy atlas consisting of a large number of galaxies using the high-resolution Chandra data and wide field XMM-Newton data. We have published the first version of the Atlas (see arXiv/1812.02718, GalaxyAtlas ) with Chandra data alone. We intend to add archival XMM-Newton data which cover the outer regions in order to have a complete view of the entire galaxy. Our main goal is to produce large-scale 2D maps of surface brightness, projected temperature, pressure and entropy as well as 3D temperature, density and mass profiles. We will then use these products to address the important issues of galaxy formation and evolution, including AGN/stellar feedback, interactions with nearby galaxies and the hotter ambient medium. We will make use of the Smithsonian high-performance computing super-cluster (Hydra) to optimally process a large number of repeated computing tasks.

The student may involve one or more sub-projects:
- X-ray image processing to optimally display high dynamic range data and to search for otherwise hidden features (e.g., by subtracting smooth 2D model, unsharp masking).
- design and develop s/w tools to analyze Chandra and XMM-data in specific purposes (e.g., for low s/n point sources, diffuse emission) either standalone or by combining with existing tools (CIAO for Chandra and SAS for XMM-Newton)
- analyze X-ray Galaxy Atlas data products for specific goals, including correlation studies, mass profiles, circum-nuclear gas and circum-galactic medium (CGM).

10. Serena Moseley (Carleton College)

ADVISOR: Dr. Chelsea MacLeod (HEA)
MENTOR: Dr. Paul Green (HEA)

PROJECT TITLE: Long-Term Variability of Nearby Quasars

Abstract: The Time Domain Spectroscopic Survey (TDSS) is accumulating approximately 2600 high-S/N spectra of nearby quasars that were observed before by the Sloan Digital Sky Survey about a decade ago. These spectra will be used to study the long-term variability of the broad Balmer emission lines on rest-frame time scales of several years, which corresponds to the dynamical time of the broad-line region. The variability patterns will be used to test models for the dynamics of the gas in the quasar broad-line regions. The student's work will be to examine the variations in the available spectra and identify and classify the variability patterns. The inspection and classification will first be done by eye and then by making measurements of the Balmer emission lines. This work will give the student the opportunity to learn about manipulation of optical spectra, programming, and the basics of the physics of the gas in quasar broad-line regions.

11. Lily Whitler (Arizona State University)

ADVISOR: Dr. Charlotte Mason (OIR; Hubble & CfA Fellow)
MENTOR: Dr. Charlie Conroy (OIR)

PROJECT TITLE: Measuring the Timeline of Cosmic Reionization

Abstract: We cannot see the first galaxies which formed in the universe, but we can observe the impact they had on their surroundings. In the universe's first billion years the majority of hydrogen transitioned from neutral to ionized. This process, Reionization', was probably caused by photons from the first galaxies, and is an exciting frontier of observational and theoretical astrophysics. The Hubble Space Telescope and biggest telescopes on the ground can observe galaxies at the end of Reionization. By studying these galaxies and how they are affected by Reionization we can learn how Reionization started and about the nature of the very first galaxies.

This project combines theoretical modeling and analysis of observations. The student will use a theoretical model of Reionization which predicts the properties of galaxies at our observational frontiers, using a combination of analytical techniques and large-scale simulations. The student will update the model using Python code to explore how the connections between dark matter and galaxies impact Reionization. The model will then be compared with existing observations of galaxies using statistical techniques to measure the timeline of Reionization. These results will be be pivotal in understanding how Reionization took place, and thus the properties of the first galaxies.

## 2018 Interns

#### 1. Courtney Bishop (College of William and Mary)

ADVISOR: Dr. Anna Rosen (RG)
MENTOR: Dr. Alyssa Goodman (RG)

PROJECT TITLE: Producing Synthetic ALMA Observations of Massive Star Forming Molecular Cores

Abstract: Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Massive star forming regions in our galaxy are rare, distant, and highly obscured making the earliest moments of their formation difficult to capture. However, large-scale high- resolution radio interferometers such as ALMA are now making it possible to capture these early phases with molecular line observations (e.g., molecular lines like 13CO and SiO). In this project, we would like to have an REU student produce mock molecular line observations from 3D adaptive mesh refinement (AMR) radiation hydrodynamic simulations of the collapse of massive pre-stellar cores into massive stellar systems. These simulations include stellar feedback - the injection of momentum and energy into the interstellar medium by young stars - from the stellar radiation field and collimated protostellar outflows. These processes shape the gas dynamics of the collapsing core. The student will use python, yt (a visualization software for AMR simulations), RADMC-3D (a radiative-transfer calculation code), and CASA (a data post-processing code for sub-mm and radio observations) to make synthetic molecular line maps from our simulation outputs. The student will then analyze their post-processed images to determine morphological features of the entrained gas in the outflows and the accretion disk properties, and also develop new diagnostics to analyze molecular line data for massive star forming regions.

#### 2. Jacqueline Blaum (Iowa State University)

MENTOR: Dr. Matthew Ashby (OIR)

PROJECT TITLE: Constraining Star Formation in the Milky Way with Machine Learning

Abstract: A comprehensive picture of star formation in the Milky Way requires an accurate census of all young stellar objects (YSOs) in star-forming molecular clouds. However, current infrared YSO catalogs are built from images where sources are spatially blended together, while their identification as young stars is ambiguous, which translates into incomplete catalogs. There are two primary causes for this incompleteness: 1) the loci of YSOs in widely used infrared color-color or color-magnitude diagrams often overlap with other kinds of sources leading to ambiguous classifications, and 2) the clustering of sources makes it difficult to identify them individually within large beams. The goal of this summer project is to more accurately reclassify a sample of intrinsically red young stellar object (YSO) sources in the Spitzer, WISE, and Herschel catalogs and to produce a new census of young stellar sources using modern techniques of astrostatistics and machine learning. The student will work with Drs. Rafael Martinez-Galarza and Matthew Ashby to select a suitable sample of infrared sources and perform an improved classification using two new algorithms that we developed 1) a machine-learning (ML) algorithm for supervised classification and unsupervised outlier detection, and 2) a deblending method for spatially clustered sources. Using the results from this analysis, the student will produce multi-wavelength SEDs of individual young stars in clustered environments and physically characterize these objects. This will allow us to construct the YSO luminosity function in the Galaxy and reveal environmental dependencies of the star formation properties, and also to test competing theories of star formation by comparing their predictions with our derived set of properties (mass, age, optical extinction, etc.). A new picture of star formation in the Milky Way will emerge from this summer experience.

#### 3. Thomas Boudreaux (High Point University)

ADVISOR: Dr. Idan Ginsburg (TA Division)
MENTOR: TBD

PROJECT TITLE: Exploring the Dynamics of Globular Clusters

Abstract: Despite over 150 confirmed globular clusters around the Milky Way, a generalized model of cluster expansion and mass evaporation rates has yet to be developed. Numerical studies have focused on the affects of external tidal fields and stellar evolution, two properties which models now suggest play important roles in shaping the long term evolution of a cluster. Moreover, a link has been suggested between the primordial binary fraction and a cluster's core radius expansion rate. While there are hints this link may exist, there has yet to be a firm quantitative relation discovered. Using the publicly available Nbody6++GPU code, we directly integrate a cluster core consisting of 1000 bodies (total mass of 516 Solar) over 500 Myr in order to find such a relation.

#### 4. Ivalu Christensen (Lund University; self-funded)

ADVISOR: Dr. Nimesh Patel (RG)

PROJECT TITLE: Probing the chemistry in low- and high-mass protostars with the SMA

Abstract: Studying the chemical composition of star forming sites can further develop our understanding of the physics of star formation. For this project, a low mass protostellar system, IRAS 16293-2422, and a hot core in high mass star-forming region G35.20-0.74N are studied. SMA data obtained in 2009 and 2011 of these objects will be imaged and the spectra will be analyzed using the Cassis software with the purpose of identifying the organic composition of both star-forming regions and comparing them. Furthermore, the LTE column densities and excitation temperatures will be characterized for selected lines.

#### 5. Sierra Dodd (University of Washington)

MENTOR: Ben Roulston

PROJECT TITLE: Characterizing Stellar Variables in the Time Domain Spectroscopic Survey

Abstract: The Time Domain Spectroscopic Survey (a subprogram of SDSS-IV eBOSS) obtains classification/discovery spectra of photometric variables selected from PanSTARRS and SDSS multi-color lightcurves. Tens of thousands of TDSS spectra are already available, and classified both via pipeline and by visual inspection. About half are quasars, and half stars. Variable star types include RR Lyr, close eclipsing binaries, CVs, pulsating white dwarfs and other exotic systems, but spectral class is usually insufficient to determine the cause of variability. The REU student will obtain richer public multi-epoch lightcurves for brighter (r<19.5) stars from the Catalina Sky Survey and Palomar Transit Factory Surveys, and run a variety of lightcurve analyses to constrain variable type, both for broad statistics relevant to future variability surveys like LSST, and to characterize the variable stars in TDSS for future classification.

#### 6. Tenley Hutchinson (Spelman College)

MENTOR: Dr. Daniel d'Orazio (TA)

PROJECT TITLE: Identifying the precursors of compact-object mergers

Note: Ms. Hutchinson's poster describing this work won the Chambliss award at the Seattle AAS meeting.

Abstract: One of the most exciting developments in astronomy and astrophysics during the past century has been the discovery of gravitational-wave-induced mergers of double black holes and double neutron stars. These discoveries have validated important features of general relativity. As more events are detected we will learn a great deal about stellar remnants and the properties of matter in extreme environments.
An important question is whether we can detect evidence of close binaries that will merge, long before the merger event happens. During the past year we have developed a framework to predict pre-merger signals at X-ray wavelengths. These signatures are of novel and exciting types, and include possible gravitational lensing of one compact object by the other.

Such signatures are expected if at least one of the compact objects slated for merger is bright during part of the pre-merger evolution. The compact objects could be luminous at early times due to a fallback disk, for example. Or they could be bright because they are accreting matter, perhaps from a companion in a wider orbit. In either case, we expect distinctive features at X-ray wavelengths which include gravitational lensing effects, where one compact object lenses its companion, that produce short-lived, repeated spikes in the X-ray emission. Dozens of already-observed X-ray sources in each of several external galaxies, and up to 1000 in the Local Group (1500 to 2000 sources in total) are bright enough that these signals are potentially detectable. This number is large enough that detections are expected and, if we do not discover systems fitting the predicted profiles, null results would be meaningful.

The goal for a student working on this project would adopt is to examine archival data from the Chandra X-ray Observatory, XMM-Newton, and several other missions to search for evidence of double-compact-object binaries in which one or both components are bright at X-ray wavelengths. The student would have the opportunity to work directly with the data, and also to assess the significance of any detected signals or null results. Skills that would become part of the student's repertoire are familiarity with accessing large archived data sets, and signal processing. The student would become comfortable with the physics of accretion, X-ray emission, and gravitational lensing. We anticipate at least one publication would come from this work.

#### 7. Amalya Johnson (Columbia University)

MENTORs: Dr. Brad Snios (HEAD) and Dr. Ralph Kraft (HEAD)

PROJECT TITLE: AGN Feedback in Brightest Cluster Galaxies

Note: Ms. Johnson described this work in a press briefing at the Seattle AAS meeting. You can watch it at the 17:10 mark of the Black Holes and Galaxies Near & Far session.

Abstract: Powerful radio sources at the centers of galaxy clusters play a key role in regulating star formation in the very massive galaxies that host them. Jets from the central supermassive black (SMBH) hole heat surrounding gas, while gas that cools from the hot cluster atmosphere can form stars and feed the SMBH. Cooled gas that falls into the SMBH boosts the jet power, leading to more heating. In this way, jet heating is linked to cooling and star formation in a feedback loop. To understand this process, we must understand how a central radio source interacts with it cluster atmosphere.

Cygnus A is by far the most powerful radio galaxy in the local Universe and it is hosted by a cluster central galaxy. Each radio lobe of Cygnus contains a compact primary hotspot and a brighter secondary hotspot, where the radio jets impact the cluster atmosphere. A very deep X-ray image of Cygnus A has revealed an almost circular "hole" surrounding the primary hotspot in the eastern radio lobe. The aim of the project is to determine the properties of this hole in order to understand how it was formed and what it tells us about the interaction between the radio source and its environment. This will involve analyzing X-ray data and applying theory to interpret the results.

#### 8. Megan Masterson (Case Western Reserve)

MENTOR: Dr. Felipe Santos (HEAD)

PROJECT TITLE: Chandra Observations of a Merging Galaxy Cluster at z>0.5

Note: Ms. Masterson's poster describing this work won the Chambliss award at the Seattle AAS meeting.

Abstract: Galaxy clusters are the most massive virialized structures in the Universe. They are the signal peaks in the cosmic density and thus have been appreciated as powerful cosmology tools. In the cold dark matter paradigm, clusters are assembled hierarchically via mergers, the most energetic events in the Universe. For this project, the student will analyze 40 ks Chandra/ACIS observations of the z=0.51 cluster G211.21+38.66, which has an unusual binary structure. The student will also make use of available SDSS data. In combination, the Chandra and SDSS data will constrain the intracluster medium temperature, density, and metallicity, among other properties of this distant system. By comparing these fundamental properties to those of relatively nearby clusters, it will be possible to gain a much better understanding of the growth of galaxy clusters.

#### 9. Evan Nunez (Cal State Polytechnic University Pomona)

ADVISOR: Dr. Joel Leja (OIR)
MENTOR: Dr. Charlie Conroy (OIR)

PROJECT TITLE: Using Distant Galaxies with Extreme Chemical Conditions as Laboratories for Stellar Theory

Abstract: current theoretical models for the evolution of massive stars are very uncertain: specifically, different theoretical models predict outputs of high-energy photons which vary by factors of two or more. It is critical to constrain this ionizing photon budget as this budget is necessary to interpret many important observations, ranging from estimates of galaxy star formation rates to the energy budget for nebular line emission to the reionization rate of the Universe. It's impossible to use nearby stars in the Milky Way to discern between these competing models, because at high metallicities the model predictions converge. However, distant galaxies with low metallicities and recently truncated star formation histories may be provide an ideal testing lab. The student will use multiple cutting-edge stellar evolution codes to identify the ideal candidate galaxies. A successful project will lead to an exciting spectroscopic campaign providing spectroscopic follow-up of these galaxies.

#### 10. Osase Omoruyi (Yale University)

ADVISOR: Dr. Elaine Winston (OIR Division)
MENTOR: Dr. Joseph L. Hora (OIR Division)

PROJECT TITLE: Studying Star Formation in the Outer Galaxy

Abstract: Star formation in the outer Milky Way Galaxy has not been as extensively studied as star formation in the inner Galaxy. Home to low gas density, low metallicity levels, and sparsely distributed molecular clouds, the outer Galaxy's environment contrasts with the gas-rich and high--metallicity environment prevalent in the inner Galaxy. By extending the study of star-forming regions to include sites in the outer Galaxy, we will obtain a more complete understanding of star formation in the Milky Way and how the process depends on environmental factors. Here, we use infrared observations from NASA's Spitzer Space Telescope and the Wide-field Infrared Survey Explorer to examine a so-far marginally-studied star-forming region in the outer Galaxy centered at (l, b) = (92.36, 1.97). Within this region, we search for and classify young stellar objects to provide insights into their parental molecular clouds, including the presence of sub-clustering, the relative ages of those sub-clusters, and whether any external triggering is likely to have occurred. We then use models to estimate the masses of the identified young stars and their disks, and compare our results to star-forming regions in the inner Galaxy.

#### 11. Aldo Sepulveda (University of Texas San Antonio)

ADVISOR: Dr. Luca Matra (RG)
MENTORs: Dr. David Wilner, Dr. Karin Öberg

PROJECT TITLE: Locating exocometary belts around nearby stars

Abstract: Belts and rings of exocomets like our Solar System's Kuiper belt (also known as debris disks) are found around at least 20% of nearby stars like the Sun. Their comets are the most untouched relics of the building blocks that went to form planets in planetary systems. Observing where these belts are located in any given planetary system and studying their structure informs us about the presence of planets and their formation conditions.
This project aims at measuring the precise location of an exocometary belt around a nearby star, using new millimeter-wavelength observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Submillimeter Array (SMA) telescopes, obtained as part of the REASONS (Resolved ALMA and SMA Observations of Nearby Stars) survey. The project will involve processing and analysis of an observation of an exocometary belt, as well as using a simple model to fit the data and derive an accurate measurement of its location within the planetary system. The goal is to understand why cometary belts including our own Kuiper belt form at specific locations within planetary systems, and pin down what physical conditions in the planet formation environment make these locations special.

## 2017 Interns

Bridget Andersen (University of Virginia)

ADVISOR: Dr. Ian Stephens (RG Division)
MENTORS: Drs. Phil Myers, Sarah Sadavoy (RG Division)

PROJECT TITLE: The Mass Evolution of Protostellar Disks and Envelopes in the Perseus Molecular Cloud

Abstract: In the typical model for low-mass star formation, a dense molecular cloud of gas and dust undergoes gravitational collapse to form a protostellar system consisting of a new central star, a circumstellar disk, and a surrounding envelope of remaining material. In this basic model, the mass distribution of the system evolves as matter accretes from the large scale envelope through the disk and onto the protostar. While this general picture is supported by simulations and indirect observational measurements, the specific timescales related to disk growth and envelope dissipation remain poorly constrained. The goal of our study is to conduct a rigorous test of a method introduced by Jørgensen et al. (2009) that uses data from the Submillimeter Array to obtain observational mass measurements of disks and envelopes around embedded protostars. Using data from the recent Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey, we derive disk and envelope mass estimates for 59 protostellar systems in the Perseus molecular cloud. We compare our results to independent disk mass measurements from the VLA Nascent Disk and Multiplicity (VANDAM) survey and find a strong linear correlation, validating the efficacy of the Jørgensen et al. method. Then, leveraging the unprecedented size and uniformity of our sample, we find no significant trend in protostellar mass distribution as a function of age, as approximated from bolometric temperatures. These results may indicate that the disk mass of a protostar is set near the onset of the Class 0 protostellar stage and remains relatively constant throughout the Class I protostellar stage.

Aliza Beverage (University of Minnesota)

ADVISOR: Dr. Howard Smith (OIR Division)
MENTOR: Dr. Matthew Ashby (OIR Division)

PROJECT TITLE: A Multiwavelength Analysis of AGN and Star Formation in Colliding Galaxies

Abstract: Galaxy mergers are key components in galaxy evolution, generally causing massive starbursts and AGN. We have gathered photometry for a sample 103 merging galaxies outlined in Brassington et al. 2015 that span wavebands from the UV to the FIR. We will review the data for these galaxies to complete their SEDs and then model their key characteristics including: star formation rate, specific star formation rate, dust mass and temperatures, and AGN contribution. The study will also address how well the simulations are able to reproduce the observed behaviors of these systems.

Jane Bright (Denison University)

ADVISOR: Dr. Guillermo Torres (SSP Division)

PROJECT TITLE: Accurate Stellar Parameters for Eclipsing Binaries, and Tests of Stellar Evolution Theory

Abstract: Eclipsing binary star systems are the best source of accurate measurements of masses and radii of stars. We use spectroscopic and photometric data from the eclipsing binary V2154 Cyg to derive the best stellar parameters for the system. These parameters can then be compared to stellar evolution models. V2154 Cyg is of particular interest because the smaller of the two stars is of the size where models often predict radii that are too small, which is thought to be caused by stellar activity not present in the models. Our accurate measurements of the stellar parameters of the stars in V2154 Cyg will allow us to test models of stellar structure and evolution.

Jenny Calahan (University of Arizona)

ADVISOR: Dr. Joseph Hora (OIR Division)
MENTOR: Dr. Howard Smith (OIR Division)

PROJECT TITLE: Clusters of Young Stellar Objects in the Cygnus-X Infrared Dark Clouds

Abstract: The Cygnus-X region is a vast star formation environment, filled with every stage of star formation from dense molecular clouds to evolved protostars. We hope to further understand the process of star formation by observing clustering patterns and masses of molecular clouds as compared to later stage young stellar objects (YSOs). In order to identify clusters of dense clouds, we will write a python script to automatically sort regions of smaller dense clouds into larger groups across the entire Cygnus-X complex. We will also utilize SED information of YSOs as found in Cygnus-X by the IRAC and MIPS instruments on Spitzer in combination with Herschel data. Using the observed SEDs we will use SEDfitter to find predictions of the mass and luminosity of each YSO which we can then compare to previously calculated molecular cloud masses.

Yijia Li (Nanjing University)

MENTOR: TBD

PROJECT TITLE: Characterizing recent outbursts from Active Galactic Nuclei (AGN) in early-type galaxies

Abstract: We have used Chandra X-ray observations of relatively nearby early-type galaxies (those within about 50 Mpc of our Milky Way), to select galaxies that show evidence of an outburst from a supermasssive black hole at the galaxy's center. Usually the outburst generates cavities that we can see in the galaxies' hot X-ray-emitting coronae. By measuring the size of the cavities and the distance of the cavities from the galaxy center, we can determine the amount of energy released from the supermassive balck hole to produce the cavities and can measure when the outburst began. This project will require first "cleaning" and "merging" individual Chandra observations, then identifying any "point" sources that need to be omitted from the analysis, measuring the spatial distribution of gas in the hot halo, by first generating a surface brightness profile of the gas, measuring the gas temperature, and then measuring the sizes of cavities in the hot halos and their distances from the galaxy center which will be used to calculate when the supermassive blackhole outburst occurred and how much energy was released.

Gautam Nagaraj (North Carolina State University)

MENTOR: Dr. Francesca Civano (HEAD)

PROJECT TITLE: Measuring Black Hole Masses for Active Galactic Nuclei (AGN) in the Chandra Cosmos Legacy Survey

Abstract: In recent decades, a strong correlation between supermassive black hole (SMBH) masses and the masses, luminosities, and velocity dispersions of the host galaxies has been established for the local universe. One of the most important questions in extragalactic astronomy is whether the correlation extends to higher redshifts (back in time): was the coevolution of black holes and galaxies constant or a complex function of time, environmental conditions, and AGN feedback mechanisms? While quasars, the highest-luminosity AGN, have been studied extensively at a large range of redshifts, faint AGN, which are at least 20 times more common in the universe, have not, and we still do not know if they have similar histories to quasars. The Chandra Cosmos Legacy Survey observed 4016 X-ray sources, mostly faint AGN. Marchesi et al. (2016) identified optical/IR counterparts to 97% of these sources, and with spectra from large optical surveys such as the Sloan Digital Sky Survey, we are using the technique of reverberation mapping to determine the masses of hundreds of SMBHs in Broad-Line AGN.

Hannah Richstein (Texas Christian University)

MENTOR: Dr. Scott Randall (HEAD)

PROJECT TITLE: Chandra Mapping of a Non-Cool-Core Cluster out to the Virial Radius

Abstract: Galaxy clusters are the largest known gravitationally bound structures in the Universe, often containing thousands of galaxies. These clusters can be classified as either cool cores (CC) or non-cool cores (NCC), depending on their temperature profiles, cuspiness, and other properties of their intracluster media (ICM). A growing number of clusters are found to be NCC clusters, but it is unclear how they are formed. We have been awarded deep Chandra X-Ray observation to probe the ICM properties of a massive NCC cluster, Abell 586, to the virial radius. With these data we aim to examine how NCC clusters are produced, and specifically what role major mergers could play in the process.

Jasmine Sinanan-Singh (Harvard University)

MENTOR: Dr. Laura Brenneman (HEAD)

PROJECT TITLE: Investigating Black Hole Spins at High Redshift

Abstract: Supermassive black hole (SMBH) spin encodes vital information about the history of SMBH growth. Examining spin over different redshifts will help us understand SMBH growth over cosmic time, an important part of understanding how SMBHs and their host galaxies evolved over time. We average the X-ray spectra of AGN from the Chandra-COSMOS Legacy Survey in different redshift bins and compute the average Fe K-alpha emission line at rest frame. We derive our method from Corral et al. (2008) to compute the rest-frame averaged X-ray spectrum and test this method on the two brightest sources in the Chandra-COSMOS Legacy Survey. We do not fit complex models to individual spectra, but rather increase the signal-to-noise ratio by averaging the spectra and then fitting to a model. For the redshift bin z=0.8-0.9, we detect an average Fe K-alpha iron emission line around 6.52 keV with a width of 220 eV and an equivalent width of 310 eV. We have tested and applied our method to a subsample of the Chandra-COSMOS Legacy Survey. Our results are in agreement with results found in Corral et al. (2008). The next step is to compute the average iron lines for the other redshift bins out to z~6.

Jamie Sullivan (University of Texas at Austin)

ADVISOR: Dr. Alex Wiegand (TA Division)
MENTOR: Dr. Daniel Eisenstein (OIR Division)

PROJECT TITLE: Minkowski Functional Analysis of the Completed Sloan Digital Sky Survey III Galaxy Map to Further Constrain Non-linear Structure Formation

Abstract: Galaxy correlation functions are one of the primary statistical tools used to extract a characterization of the large-scale structure of the universe. The higher-order correlation functions reveal the strongly non-Gaussian nature of the galaxy distribution, but are quite difficult to compute. Through the use of Minkowski functionals we exploit both the topology and geometry of the distribution to efficiently compute the higher-order functions. By applying this analysis to the full SDSS-III Luminous Red Galaxy dataset, we will produce an unprecedented accuracy in the Minkowski Functionals. Results of this analysis will be used to probe the redshift evolution of these galaxies, and possibly to constrain cosmological model parameters.

Abygail Waggoner (Ball State University)

ADVISOR: Dr. Ilse Cleeves (AMP Division)

PROJECT TITLE: Chemical Processes in Protoplanetary Disks

Abstract: Protoplanetary disks are a natural outcome of the formation of a young star, with the star at the center of the disk. In its young age, the star emits strong flares of X-ray radiation whose strength depends on the mass of the star and the strength of the stellar magnetic fields. The X-rays penetrate the disk, especially in the surface layers. These layers are composed of dust grains, atoms, molecules, ions, and some ices, which chemically respond to the flare. This project aims to understand 1) which molecules and atoms respond most strongly to X-ray flares emitted from a T Tauri star, 2) what are the long term (Myr) and short term (days to years) effects on chemical abundances in the disk, and 3) how do the chemicals react in different vertical layers and at varying distances from the star. The results of this theoretical exploration will provide testable predictions for future ALMA observations of time-domain chemistry.

David Zegeye (Haverford College)

MENTORS: Drs. Guiseppina Fabbiano, Andreas Zezas (HEAD)

PROJECT TITLE: The Evolution of Galaxies through the Spatial Distribution of Their Globular Clusters: the Brightest Galaxies in Fornax

Abstract: Globular Clusters (GCs) are compact objects that possess 10^4 to 10^6 gravitationally bound stars. GCs are ideal proxies to reconstruct the evolution of their host galaxies, because many properties of the population of GCs are determined by the host galaxy growth. Measurements of GC distributions reveal spatial, overly dense structures in their host galaxy that may have resulted from major mergers or satellite galaxy accretion. In recent years, significant research on the spatial distribution of GCs has been performed for galaxies found in galaxy clusters. D'Abrusco et al. (2016) investigated the large-scale structure of the spatial distribution of intracluster GCs in the core of the Fornax Cluster, using ground-based data. This project will continue the study of globular cluster distribution for galaxies in the Fornax Cluster, by using data produced by the Advanced Camera for Surveys on the Hubble Space Telescope in order to provide more insight into the evolutionary history of their host galaxies.

## 2016 Interns

Colloquium schedule | Aug 11 Symposium Program AAS Abstracts Summer Calendar

Kaley Brauer (Brown University )

ADVISOR:Dr. Saku Vrtilek (HEA Division)
CO-ADVISORS/MENTORS: Dr. Mike McCollough (OIR Division)

PROJECT TITLE: The Structure of Cygnus X-3

Abstract:
We have infrared data of Cygnus X-3 obtained with the Gemini North telescope in Hawaii. The student will help reduce and analyze the data. We will construct Doppler tomograms (a method similar to medical cat scans) to image the structure of the system. We also have scheduled observations this summer of a Fermi source recently identified as an XRB using a Magellan telescope in Chile.
What the student will learn: About optical telescopes, and how astronomical data are obtained and reduced, as well as sSome physics and mathematics related to binary stars and tomography. There will be a paper on which the student will be listed at least as co-author.

Jeremy Dietrich (Harvard University)

ADVISOR:Dr. Howard Smith (OIR Division)
MENTORS: Drs. Rafael Martinez-Galarza, Matthew Ashby (OIR Division)

PROJECT TITLE: SEDs of Interacting Galaxies

Abstract:
Colliding galaxies are not only dramatic events, they are vital evolutionary processes in the cosmic order, facilitating the production of stars and their essential by-products. Observations suggest that the most luminous galaxies during the cosmic epoch of peak star formation are powered by the energetics of star formation, and are apparently the result of galaxy mergers. Because they are bright, these luminous galaxies are becoming increasingly important to understand as new telescopes find more of them, stretching back to the epoch of reionization. In the past decade, space missions from the ultraviolet to the far-infrared have enabled the measurement of the full spectrum of merging galaxies from the ultraviolet radiation of hot young stars to the submillimeter light emitted by dust heated by absorbed UV. We are in the midst of a detailed accounting of the spectral energy distribution (SED) of nearby merging galaxies to improve our understanding of merger processes. We study a range of merger stages, and model the SED shapes to retrieve key parameters such as the star formation rates and dust properties. We have simultaneously undertaken a series of merger simulations and applied the models to the simulated SEDs to test the credibility of the analysis method while improving the simulation inputs. Four important issues are highlighted: the role of a black hole nucleus in contributing to a galaxy's luminosity, the accurate accounting of the mass in cold dust, the reliability of simple-minded star formation metrics like the Schmidt-Kennicut relation, and the reality of the so-called �galaxy main sequence� which correlates a galaxy's star formation rate with its mass. ^M^MIn this project, the student, building on our prior analysis of 31 merging systems, will extend to sample to include many more dramatic, late-stage mergers, and then work to assemble the largest complete sample of merger SEDs available. The student will work on state-of-the-art computer systems to analyze data from recent space missions from GALEX to Herschel, with some emphasis on the infrared datasets. The results will likely lead to one or more publications.

Callie Hood (University of North Carolina)

ADVISOR: Dr. Jayne Birkby (SSP Division)
CO-ADVISORS/MENTOR: Dr Mercedes Lopez-Morales (SSP Division)

PROJECT TITLE: Exoplanets in high resolution: hunting for molecules in the atmospheres of hot giant exoplanets

Abstract:
High-resolution spectroscopy enables the direct detection of the spectra of exoplanet atmospheres. From this, we can learn about their chemical make-up, study their structure including clouds and stratospheres, and measure their global wind patterns along with the length of their exo-days. In this project, we will analyze spectra from a program observed at the Very Large Telescope in Chile, using the high-resolution spectrograph ARIES, to study the atmospheric properties of large hot exoplanets. This technique is a forerunner for detecting biomarker gases in the atmospheres of Earth-like planets with the giant segmented mirror telescopes which will be commissioned in the 2020s. This project will give the student experience in i) the processing of high-resolution infrared echelle spectra, ii) coding algorithms to detect very faint exoplanet signals via cross-correlation with laboratory models of molecular spectra, iii) an insight into the exciting and rapidly evolving field of exoplanet atmospheres, and iv) the opportunity to propose new and exciting targets for upcoming observations for a new high-resolution program with ARIES at the MMT in Tucson.

Luan Luan (Nanjing University)

ADVISOR: Dr. Christine Jones (HEA Division)
CO-ADVISOR: Dr. Akos Bogdan (HEA Division)
PROJECT TITLE: The X-ray Point Source Population in M87

Abstract:
The giant elliptical galaxy M87 lies at the center of the Virgo galaxy cluster. Very deep Chandra X-ray observations show a large population of point sources in M87, most of which are likely to be low-mass X-ray binaries, although some will be background AGN. With the Chandra observations, we will be able to measure the luminosity function of the X-ray sources in M87, compare Chandra observations taken at different times to look for X-ray transients, and identify X-ray sources associated with globular clusters. We will compare the results for M87 with studies done for less massive galaxies, particularly the Sombrero galaxy and Centaurus A.

Chima McGruder (University of Tennessee)

ADVISOR: Dr. Guillermo Torres (SSP Division)
PROJECT TITLE: Accurate Stellar Parameters for Eclipsing Binaries, and Tests of Stellar Evolution Theory

Abstract:
The goal of the project is to derive very accurate absolute masses, radii, temperatures, and other parameters for the components of an eclipsing binary for the purpose of using these measurements to test current models of stellar structure and evolution. One possible target for this investigation is V541 Cyg, a high-mass eclipsing system that shows changes in the orbital elements due to apsidal motion. This adds interest to the study because the rate of apsidal motion can be predicted by theory, providing a further test. Another possible target is V2154 Cyg, which is interesting because it is a triple system. While this can complicate the analysis, the fainter component of this triple system is a low-mass star, and as such it provides an important test of models in a regime in which they have shown disagreements with previous observations. These disagreements are not yet well understood, but are possibly related to chromospheric activity. The work will involve analyzing high-resolution spectra to determine the radial velocities of all components of the target system (two for V541 Cyg, or three in the case of V2154 Cyg) as well as the elements of the spectroscopic orbit. This will use sophisticated two- or three-dimensional cross-correlation techniques. The project will also require an analysis of the light curves of the eclipsing binary (already in hand) with specialized software to derive the geometric properties of the system, necessary to compute the sizes of the stars and other characteristics. This investigation will provide an opportunity to learn about stellar astrophysics, stellar evolution models, and how to compare them with the measurements described above.

Luis Nunez (Cal State Pomona)

ADVISOR:Dr. John Johnson (SSP Division)
PROJECT TITLE: Small Friends of Hot Jupiters

Abstract:
Hot Jupiters are gas giant exoplanets with periods less than 10 days. These planets have previously been assumed to have formed at several astronomical units, like our own Jupiter, and somehow had their semimajor axes shrunk (the process of migration). However, new theories predict that hot Jupiters can form right next to their host star through the collision of large Earth-sized planetesimals (arxiv:1511.09157). A direct prediction of this new class of models is that hot Jupiters should be accompanied by small planets in similarly short-period orbits. This has been observed in the WASP-47 system (arXiv:1508.02411), which contains a hot Jupiter and two "super-Earths" with periods less than 10 days. Since most hot Jupiters have been detected, or confirmed in the case of transiting planets, using low-precision radial velocities, it is possible that small planets lurk "in the shadows" of known hot Jupiters. The summer student will analyze extant radial velocity data and plan future observations to detect or place limits on these small friends of hot Jupiters.

Imad Pasha (University of California, Berkeley)

ADVISOR:Dr. Reinout van Weeren (HEA Division)
CO-ADVISOR: Dr. Christine Jones (HEA Division)

PROJECT TITLE: A search for lensed X-ray sources behind massive galaxy clusters

Abstract:
The aim of the project is to search for lensed X-ray AGN behind massive galaxy clusters observed with Chandra and HST. The detection of lensed X-ray sources would enable the study of intrinsically faint and distant objects that would remain undetected without the power of lensing. Even more exciting would be the detection of a multiply lensed X-ray source. If such a source is time variable, it would provide strong constraints on the mass model of the cluster and it would also allow us to study the expansion of the Universe. Only four lensed X-ray AGN are known so far, with relatively modest amplification factors, but no systematic searches have been carried out. A good starting point for a search would be CLASH galaxy cluster sample as HST images, photo-z catalogs, and lensing models are publicly available (https://archive.stsci.edu/prepds/clash/). Chandra has also observed most of the CLASH sample. The X-ray sources in the Chandra images can thus be cross-matched with the HST catalogs to find lensed objects. Chandra's high spatial resolution is essential for this project so that one can locate the optical counterparts and reduce the Poisson noise of the X-ray emitting intracluster medium.

Samantha Scibelli (Stony Brook)

ADVISOR: Dr. Volker Tolls (OIR Division)
CO-ADVISOR/MENTOR: Dr. Howard Smith (OIR Division)

PROJECT TITLE: Search for Star Formation in Inner Galactic Gas Clouds

Abstract:
In our Galaxy we have huge reservoirs of dust and gas in the spiral arms fueling star formation. Some of this material eventually falls into the inner regions of the Galaxy, where the bar is located. Here, the gas and dust form large clouds, the inner galactic gas and dust clouds (IGGC), which move along semi-stable x1-orbits and spiral into the center of the Galaxy. Further inward, they will collide with gas and dust clouds on the central 100 pc ring, where they are expected to undergo rapid star formation in regions like Sgr A, B, C, and D. The question is: although the IGGCs are very dense, no HII regions have been found indicating star formation. Why?
We have mapped several of these clouds in the region called Clump 2 with the Herschel Space Observatory and retrieved additional archival ground-based observations. The goal for this summer project is to determine the basic properties of one of these clouds, IGGC 19/23, which shows several distinct hot cores. This project will combine Herschel spectroscopic and photometric data with observations from the Spitzer Space Telescope and ground-based spectrscopy of molecular lines. The primary part of the project will be to identify individual cloud cores, to extract their physical conditions, to search for signs of star formation activity (e.g., outflows), and to compare the results to findings for similar cores as documented in the literature to understand why these cores might be different.

Andrew Sevrinsky (Georgia State University)

ADVISOR: Dr. Michael Dunham (RG Division)

PROJECT TITLE: Evidence for Episodic Accretion in Protostars

Abstract:
Stars form from the gravitational collapse of dense molecular cloud cores. The gravitational energy released during this collapse is radiated away as accretion luminosity. A longstanding problem in star formation is that this accretion luminosity is much too low, implying accretion rates much too low to actually form stars. A possible solution to this problem is "episodic accretion", where the accretion rate onto a star is usually much lower than average but occasionally much higher, such that the mean rate remains about the same and a star of a given mass forms in about the same amount of time.
In this scenario, which represents a paradigm change in our understanding of how stars gain their mass, a forming star (called a protostar) is much more likely to be observed in the low accretion (and thus low luminosity) state. While episodic accretion is capable of resolving the luminosity problem and is supported by indirect evidence, debate over its necessity in matching the observed luminosities of protostars remains.
In this project the student will use existing observations to calculate and compile new measurements of protostellar luminosities, while also constructing models based on existing accretion theories in order to develop theoretical luminosity predictions. By comparing the two, the student will provide the strongest test yet of both the necessity and ability of episodic accretion in matching the observed luminosities of protostars, and will thus obtain the most definitive results to date on the role of episodic accretion in forming stars.

Isabella Trierweiler (Yale University)

ADVISOR: Dr. Yuanyuan Su (HEA Division)

PROJECT TITLE: Deep Chandra Observations of NGC 1399: Sloshing fronts and AGN feedback

Abstract:
The Fornax Cluster is a poor galaxy cluster residing at 19 Mpc (1? = 5.49 kpc) and centered on a bright elliptical galaxy NGC 1399. Such low mass clusters are the main baryon reservoirs in the Universe and are the essential building blocks of the hierarchical formation. Thanks to its proximity, the Fornax Cluster has been a favorite target for many generations of X-ray missions. The cluster center, NGC 1399, displays prominent sloshing cold fronts along the west-east directions. The sloshing was probably induced by off-axis mergers which bring lower entropy gas at the bottom of a cluster potential well into contact with hotter cluster gas outside the center. The second brightest galaxy NGC 1404 is the most likely disturber in this case. NGC 1399 also harbors an active galactic nucleus (AGN) which produced X-ray cavities distributed along the north-south directions and overlapping with the radio emission. Both sloshing and AGN feedback are promising solutions to the cooling catastrophe at centers of cool core clusters. In this case, the sloshing features and that of AGN feedback are in vertical directions, the modeling of which is free from complicated degenerate interpretations of the data. Chandra, with its superb spatial resolution, allows us to study these phenomena in great detail, particularly for such a nearby object. The Fornax Cluster was observed by Chandra for 1 Ms; about 250 ksec was focused on the cluster center. The aim of this project is to quantify the properties of the sloshing fronts, the X-ray cavities, and the cool core in NGC 1399 through the analysis of the existing Chandra observations. We will determine whether sloshing or AGN feedback is more relevant to the regulation of cool cores. We will also constrain the evolution process of low mass clusters through this study.

Irene Vargas-Salazar (Louisiana State University)

ADVISOR:Dr. Cara Battersby (RG Division)

CO-ADVISORS/MENTORS: Dr. Eric Keto and Qizhou Zhang (RG Division)

PROJECT TITLE: Extreme Star Formation in the Center of our Galaxy

Abstract:
We are searching for a summer intern to investigate extreme star formation in the central region of our Galaxy. The center of our Galaxy hosts a supermassive black hole and the densest reservoir of molecular gas in the Galaxy. However, the best measurements to date suggest that this region seems to be breaking star formation laws and under-producing stars by about an order of magnitude. Is there a population of newly formed stars missed by previous observations that explains this discrepancy? Can we explain the dearth of star formation by high turbulence or magnetic fields? The student will collaborate with our Legacy Survey Team working to observe the center of our Galaxy at high resolution and long wavelengths using the Submillimeter Array. Observations from years 1 and 2 of the survey are complete, and the student will work with fully calibrated and reduced data from the survey to investigate the properties and star forming activity of clouds in our Galactic Center. In particular, the student will work with 3-D visualization tools to identify star-forming regions in 3-D. This is a relatively unexplored region of the Galaxy, with many mysteries to solve and discoveries to uncover. Understanding how stars form (or why they don't) in such an extreme environment is key to building a global model for the fundamental process of turning gas into stars.

## 2013 Interns

INTERN: Michael Calzadilla (Southern Florida University)

ADVISOR: Dr. Christine Jones (HEA Division)
CO-ADVISOR/MENTOR: Dr. Reinout Van Weeren (HEA Division)

PROJECT TITLE: The Gas Environment of AGNs in a Sample of 3CRR Radio Galaxies

Abstract:
Understanding the influences of local galaxy environment and the roles of supermassive black holes in galaxy evolution are critical. Through observations as well as numerical simulations, significant progress has been made in both of these areas. We now better understand the role of galaxy mergers and the rapid growth of black holes through radiatively efficient accretion at high redshifts, as well as the radiatively inefficient accretion modes that dominate at low redshifts. We also know the importance of AGN feedback in reheating cooling gas in galaxy centers and thus keeping elliptical-type galaxies red and dead. However, many questions about AGN accretion and outbursts remain. In particular, what triggers an outburst? What governs the power of the outburst? To address these questions, we must understand the environment near the AGN as well as the large scale environment outside the host galaxy. These environments affect the processes of how black holes are fed and grow as well as how AGN outbursts are triggered.

We will use Chandra observations to investigate the gas environments for a sample of 3CRR radio sources. Our specific goals are to measure the extent, luminosity, gas mass, and for brighter sources the gas temperature of the extended X-ray emission associated with 3CRR sources. We also will estimate gas cooling times and inflow rates and correlate these with radio morphologies and with the X-ray and radio luminosities of the nucleus.

INTERN: Benjamin Cook (Princeton University)

ADVISOR: Dr. Peter Williams (OIR Division)
CO-ADVISOR: Professor Edo Berger (OIR Division)

PROJECT TITLE: Understanding Magnetic Supersaturation in the Coolest Stars

Abstract:
Sun-like stars obey a saturated rotation/activity relationship: the faster they spin, the more magnetically active they are (as traced by observables such as radio, X-ray, and H-alpha emission) up until a point at which magnetic activity tops out. Recent data collected by our group and others, however, indicate that in the very smallest stars - M dwarfs and brown dwarfs - there is a new "supersaturation" region, in which extremely fast-spinning stars show a decrease in their magnetism. We'll work with the REU student to investigate this phenomenon using our recent data and measurements of many stars from the literature. The key goals will be to use high-quality data and analysis to rigorously establish (or reject) the existence of supersaturation and to learn about the physical basis for this effect, with the aim of presenting these results in a refereed publication. The student will learn about topics including "NoSQL" database techniques, coding, modern statistical analysis, the astrophysics of small stars, and writing up results for publication.

INTERN: Ying Feng (Penn State University)

ADVISOR: Dr Katja Poppenhaeger (HEA Division)
CO-ADVISOR/MENTOR: Dr. G. Esra Bulbul (HEA Division)
CO-ADVISOR/MENTOR: Dr. Andy Goulding (HEA Division)

PROJECT TITLE: Small Stars, Big Blasts: X-ray flares of Low Mass Stars

Abstract:
Low mass stars are prime candidates for finding exoplanets in the habitable zone. An important factor to assess the actual habitability of a planet is the frequency and intensity of magnetic flares of the host star, i.e. energetic outbursts in the stellar atmosphere which emit all over the electromagnetic spectrum. Low mass stars (M dwarfs) often produce powerful flares, and X-ray observations are very sensitive tracers for this. In this project, the summer student will reduce data from the X-ray telescope XMM-Newton to analyze flare occurrence and energetics in low mass stars. The aim is to test if there are changes in the flare-energy distribution between very low-mass, fully convective M dwarfs and more massive stars which possess a radiative core.

INTERN: Jocelyn Ferrara (Barnard College - Columbia)

ADVISOR: Dr. Matthew Bayliss (TA/ITC Division)
CO-ADVISOR: Dr. G. Esra Bulbul (HEA Division)

PROJECT TITLE: A Joint Optical + X-ray analysis of the Triple Merging Cluster, MACSJ1226.8+2153

Abstract:
Galaxy clusters form via mergers of smaller sub-clusters. During such mergers, most of the kinetic energy of the hot baryonic gas gas belonging to the colliding sub-clusters is dissipated by shocks into thermal energy of the intra-cluster medium. A particularly striking example of a cluster merger is MACSJ1226.8+2153. MACS1226, featuring a complex X-ray morphology in the cluster core, has been observed with the Chandra X-ray Telescope for 20 ks in 2003 and 130 ks in 2011. Optical observations show three distinct cluster cores, each with strong lensing features, centered roughly on the locations of three peaks in the Chandra X-ray emission. This cluster appears to be a rare triple-merger in progress.

The proposed project will be a joint analysis using publically available archival data from Chandra, HST/ACS (imaging of all three cores/X-ray peaks), along with proprietary weak lensing data (including published lensing maps from Subaru; Oguri, Bayliss et al 2012) and cluster member dynamics (>> 100 total members out to several virial radii from GMOS+Magellan,+Hectospec) that are available through Advisor Bayliss. The student will be working with the X-ray data in combination with the cluster member dynamics to look for physical evidence of the merger physics, including hints of X-ray emission from filaments between the merging clumps, sharp gas density edges and the unambiguous temperature jumps, and evidence for substructure and differential bulk motions in the cluster member galaxies across the merging superstructure. Depending on the background/skill of the student, the weak and strong lensing information will also be combined with the X-ray analysis to de-project the three dimensional shape of the individual merging clumps.

INTERN: Christina Kreisch (Washington University - St. Louis)

ADVISOR: Dr. Marie E. Machacek (HEA Division)

PROJECT TITLE: Gas Hydrodynamics in the Cores of Massive Galaxy Clusters

Abstract:
One of the key challenges facing cosmological models today is the nature of dark energy, the constituent of our universe responsible for its accelerated expansion. One powerful tool to probe its equation of state is the evolution of the distribution of masses for large scale structure, specifically galaxy groups and clusters, across cosmic time. Most of the ordinary matter in galaxy clusters is in the form of diffuse, hot X-ray emitting gas that, if hydrodynamically relaxed, traces the total gravitational potential of the cluster, and allows the measurement of the cluster's total mass. However, in current cosmological models, galaxy clusters grow by interaction and merger, and so are often not relaxed. It is vital to understand the effects of these mergers on the hydrodynamical state of the cluster gas, both to advance our models of galaxy cluster evolution and to assess how galaxy cluster properties, derived observationally, can best be used to test cosmological models.

In this project the student will use high spatial resolution data from the Chandra X-ray Observatory to perform standard X-ray imaging and spectral analysis on two massive galaxy clusters (ZW3146 and RXJ1347) in two different stages of merger, to understand how the mergers affect the hydrodynamic state (temperatures and densities) and bulk motions of the cluster gas. These observational results will be compared to existing simulations to determine merger parameters and constrain the microphysical properties of the inter-cluster medium.

INTERN: Laura Kulowski (Brown University)

ADVISOR: Dr. Huiqun Wang (AMP Division)

PROJECT TITLE: Identification and Investigation of Martian Dust Storm Source Regions from Orbital Observations

Abstract:
Global dust storms are a uniquely Martian atmospheric phenomenon. Their seemingly random occurrences in southern spring and summer have thus far eluded prediction and theoretical understanding. In addition to global dust storms, dust storms at successively smaller scales occur at increasing frequencies with regional dust storms preferentially developing in certain seasons and locations and local dust storms occurring nearly daily over the planet.

The closure of the martian dust cycle refers to the spatial and temporal scale over which the net flux (deflation vs. deposition) of dust is balanced. The length of time over which the Martian dust cycle is closed remains unknown. Understanding the variability of active dust lifting sources will observationally corroborate the predictions made by general circulation models (GCMs), and constrain the proportional role dust storms play in closing the dust cycle.

We will focus on the surface sources of dust storms on Mars by analyzing observations from the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO), and (if time permits), utilizing specific directed numerical experiments with the MarsWRF GCM to address the following science questions:
Where and what are the sources of dust storms on Mars?
What is the correlation of dust sources to surface properties?
What is the three-dimensional structure of dust in and around dust storms?
What is the impact of dust storms on future storm generation?

These questions will be addressed in four steps. First, we will examine Mars Daily Global Maps (MDGMs), produced with wide-angle images from the MGS/Mars Orbital Camera (MOC) and from the MRO/Mars Color Imager (MARCI), for locations of active dust lifting and construct a database of dust lifting locations over $5$ Mars years (MYs). Next, we will correlate these dust lifting locations to surface properties such as thermal inertia, mineralogy, topography and albedo using publically-available data. Thirdly, we will study the three-dimensional spatial structure of the dust mixing ratio within dust storms associated with the previously constructed database identified by MRO/MARCI with the MRO/Mars Climate Sounder (MCS). Finally, if time permits, using the MarsWRF GCM, we will simulate local and regional scale dust storms like those observed with MARCI at high horizontal resolution and examine the impact such a storm has on the meteorological parameters (e.g., surface wind stress) that may influence future dust storms at various scales.

This project will help constrain the martian dust cycle using currently available datasets, and aid significantly in characterizing the dynamics of atmospheric regions over daily, seasonal, and inter-annual time scales. The student will have the opportunity to gain experience in Mars data analysis and numerical modeling and knowledge of the martian surface-atmosphere system in general.

INTERN: Shengkai Alwin Mao (University of California - Berkeley)

ADVISOR: Dr. Nelson Caldwell (OIR Division)
CO-ADVISOR: Dr. Matthew Walker (TA Division)

PROJECT TITLE: Origins of Stellar Streams in the Outskirts of the Milky Way

Abstract:
According to the standard cosmological model, galaxies like the Milky Way are built 'hierarchically' by mergers and accretion of vast numbers of smaller dark matter halos, many of which should have hosted 'dwarf' galaxies. Several tens of dwarf galaxies are known to have survived, intact, to the present day and are observed as satellites of the Milky Way. Others were not so lucky and were destroyed by tidal forces, and are today visible as 'streams' of stars in the outskirts of the Milky Way. In order to understand how many of these dwarf galaxies served as Galactic building blocks -- and ultimately to study the nature of their host dark matter halos -- we have obtained high dispersion optical spectra from the MMT and Magellan telescopes for several known stellar streams. The prospective student would use a mix of standard analysis programs and newly written programs, to measure velocities and atmospheric compositions of these stars in order to determine their origins. This project gives students the opportunity to work with existing data to study the formation of the Milky Way and its relation to the properties of dark matter. As the project is ongoing, some opportunity exists for helping to obtain new data as part of a remote observing run.

INTERN: Kathryn McKeough (Carnegie Mellon University)

ADVISOR: Dr. Aneta Siemiginowska (HEA Division)
CO-ADVISOR: Dr. Vinay Kasyap (HEA Division)

PROJECT TITLE: Looking for the Signatures of Interactions between the Radio and the Intercluster Medium in Deep Chandra X-ray Observations

Abstract:
We will investigate the deep Chandra observations of a galaxy cluster with a powerful radio source in the center. The main goal is to look for signatures of interactions between the radio source and cluster environment and investigate statistical issues related to detection of such structures in X-rays. We plan to apply the advanced image analysis technique developed by the CHASC to the data to assess the significance of any detected structures. These studies are important for our understanding the feedback and the impact of the quasar on the cluster environment at high redshift.

INTERN: Amber Medina (New Mexico State University)

ADVISOR: Dr. John Raymond (SSP Division)
CO-ADVISOR: Dr. Richard Edgar (HEA Division)

PROJECT TITLE: Shock Waves in the Cygnus Loop

Abstract:
Several years ago, we worked with REU student Greg Salvesen to measure the proper motions of shock waves in the Cygnus Loop supernova remnant and compare the resulting shock velocities with electron temperatures derived from fitting X-ray spectra (Salvesen et al, 2009, ApJ, 702, 327; http://arxiv.org/abs/0812.2515). We have now obtained high resolution profiles of the hydrogen H alpha line for about 30 positions along these shocks using the HECTOCHELLE instrument on the MMT telescope. The profiles are made up of two components: The broad component is around 250 km/s wide, corresponding to a post-shock proton temperature around 2 million K, and the narrow component is about 35 km/s wide, corresponding to a pre-shock proton temperature around 30,000 K. The intensity ratio of the two components is sensitive to electron temperature. Preliminary fits to some of the line profiles show a range of broad component widths and a strong photoionization precursor ahead of the shock. The project for this summer would be a systematic study of the line profiles, including combining spectra from sets of fibers to improve signal-to-noise ratios and the study of variations in the sky background. The result should be a paper on the photoionization precursor and the relationship between the proton temperatures and shock speeds. In particular, we will compare with the surprising result of Salvesen et al. that the electron temperatures exceed those expected from the shock speeds at many positions. The student will learn about fitting procedures and uncertainty estimates, the relevant atomic processes, the physics of collisionless shock waves and supernova remnants.

INTERN: Robert T. Sutherland (Auburn University)

ADVISOR: Dr. Randall Smith (HEA Division)

PROJECT TITLE: Testing the Sensitivity of the Collisional Cooling Function to the Underlying Ion Population

Abstract:
The cooling function [L(T)] of a hot (0.1-10 keV) optically-thin collisional plasma determines how fast the plasma will cool by radiation, and is a key aspect in hydrodynamic models of supernova remnants, starburst galaxies, and galaxy clusters. Although the details of the cooling curve depend upon millions of individual atomic rates, in practice it is dominated at each temperature by emission lines from a few specific ions. The total radiative losses, therefore, depend upon the abundance of these ions and therefore their ionization and recombination rates at particular temperatures. We have a computer code (apec, written in C) that uses an atomic database (AtomDB) to calculate the cooling function. The code contains hooks that vary the input atomic rates in order to test the sensitivity of the final results to the input rates. This project would involve using apec and AtomDB to determine, as a function of temperature, which ionization and recombination rates most significantly impact the cooling curve. The final result will be the first-ever error estimate for the cooling function. More importantly, the project will determine the most important ionization and recombination rates at different energies \& temperatures, enabling targeted experimental measurements to reduce these errors.

INTERN: V. Ashley Villar (Massachusetts Institute of Technology)

ADVISOR: Professor Alicia Soderberg (OIR Division)

PROJECT TITLE: Supernova Forensics

Abstract:
For decades astronomers have studied supernovae almost exclusively in the optical bands where the bolometric luminosity peaks. However, some of the most important discoveries about stellar death have been made at other wavelengths, from radio to GeV. We will study several supernovae and their environments across the electro-magnetic spectrum to shed light on the final days, months, years in the life of a dying star.

## 2012 Interns

INTERN: Peter Blanchard (University of California - Berkeley)

ADVISOR: Dr. Matt Bayliss (TA Division)
CO-ADVISOR/MENTOR: Dr. Michael McDonald (MIT)

PROJECT TITLE: Searching for Spectroscopic Signatures of Biases in Strong Lensing Selected Clusters

Abstract:
The idea is to test for empirical evidence of astrophysical biases in a sample of galaxy clusters that are selected for their strong lensing efficiency. There is an expectation from simulations that the strong lensing selection should be connected to underlying biases in strong lensing selected clusters vs. the general cluster population, but this expectation has never been tested in real clusters.

Strong lensing galaxy clusters are a small subset of the general cluster population which have anomalously high strong lensing cross-sections. Such high strong lensing cross-sections require that the surface mass density in the cores of these clusters be much higher than typical clusters at the same mass and redshift. We like to think that we have a solid model for the evolution of large scale structure in the universe, but how we end up with strong lensing clusters - the most extremeophile population of massive structures - is still a mystery. The outstanding question here is, what causes the high surface mass density in the cores of these clusters?

There are several possible astrophysical explanations, one of the most reasonable of which is baryonic cooling processes (if baryons cool and contract efficiently in cluster cores, then they can gravitationally drag additional dark matter down into the core and increase the density). Other possible explanations are more exotic (and less likely), and include high rates of major mergers (which would pose a problem for what we think we know about merger rates of halos in simulations) or non-gaussianity in the primordial density field of the universe (which could produce an excess of exceptionally massive and concentrated clusters).

The specific project will involve grabbing SDSS spectra of brightest cluster galaxies (BCGs) for a strong lensing selected sample of clusters, and measuring spectroscopic diagnostics (primarily nebular line emission EWs, which can trace baryonic processes, such as star formation and cool core activity in BCGs) for the strong lensing clusters. This strong lensing selected sample already exists; it is a subset of a complete SDSS optical cluster sample where we have performed a systematic search (with an understood completeness) for giant arcs produced optically selected clusters, and have also performed extensive followup to characterize the purity of the resulting cluster lenses. This sample represents all clusters within a well-defined cosmological volume which are good strong lenses (producing bright giant arcs), includes >~ 200 clusters, and will be published in a paper that should appear on the arxiv by late April. Properties of the strong lensing clusters will be compared to those of the general optical cluster population (e.g. those published in McDonald 2011, ApJL, 742, 35).

INTERN: Philip Cowperthwaite (University of Maryland - College Park)

ADVISOR: Dr. Howard A. Smith (OIR Division)
CO-ADVISOR/MENTOR: Raffaele D'Abrusco (HEA Division)

PROJECT TITLE: The Unique Diagnostic Infrared Colors for Blazars: The WISE Blazar Strip

Abstract:
Blazars are AGN whose powerful relativistic jets are aimed directly towards us, and whose radiation is dominated by nonthermal processes. We have discovered that infrared colors of blazars are a powerful identification tool, and we have used this diagnostic to identify probable new blazars, including some gamma-ray sources, and to begin to address the physical mechanism(s) responsible. We have published 3 papers on this topic in the past year. From a sample of 1365 previously known blazars (from the ROMA BZCAT) observed in the first release of the WISE Preliminary Source catalog we prepared a color-color analysis; we have now added sources from the second WISE release. We find that blazars lie on a narrow strip in infrared colors, distinctly redder on average at the short bands than average stars, starbursts, and bright galaxies. The Spitzer Space Telescope Infrared Spectrometer has observed about 150 blazars as part of many various programs. We propose in this project to reduce and examine these spectra to see if (1) there are any infrared lines that might help to categorize the object; (2) any faint dust features that might help to characterize the dust disk around the throat of the nucleus; (3) model the mid-IR spectra energy shape more precisely by combining the spectral continuum with photometric datasets.

INTERN: Emmet Golden-Marx (Brown University)

ADVISOR: Dr. Matt Ashby (OIR Division)
CO-ADVISOR/MENTOR: Dr. Howard A. Smith (OIR Division)

PROJECT TITLE: Star Formation in Nearby Galaxies Measured by the PACS Instrument Aboard Herschel

Abstract:
tar formation is arguably the most important physical process in the Cosmos. It is the primary driver of galaxy evolution and the mechanism whereby heavy elements are created. Here at the CfA we are leading a project to understand how to best measure the pace and intensity of star formation taking place in nearby galaxies. This is the Star Formation Reference Survey (SFRS).

Observations of SFRS galaxies have already been carried out with a number of star formation tracers from UV to radio wavelengths. However, a significant gap exists in our knowledge of the far-infrared tracers in particular, because no one has yet analyzed the Herschel/PACS photometry for our galaxy sample, forcing us to rely more heavily on IRAS data than we would like. It is important to close this gap, because the far-infrared regime is arguably the 'gold standard' for accurate measurements of star formation rate.

The plan of our proposed project is for the student to:
1. determine which SFRS galaxies have been observed by Herschel/PACS
2. download and reduce the relevant data to measure the fluxes from our sample galaxies at 70, 100, and 160 um with the standard Herschel reduction software package known as HIPE
3. in combination with data already in hand (e.g., redshifts, other photometry), convert the fluxes to luminosities
4. compare the outcome to previous measurements with Spitzer/MIPS and IRAS to identify any deficiencies in any of the involved datasets
5. identify trends in dust temperature and star formation mode (quiescent versus starburst) within the sample so far observed by Herschel

Additionally, it may be possible for the student to compare the outcome to tracers of star formation collected by SFRS team members at other wavelengths, e.g., UV imaging from the GALEX satellite and near-infrared photometry from Spitzer.

INTERN: Margaret Landis (University of Northern Arizona)

ADVISOR: Dr. Catherine Espaillat (RG Division)

PROJECT TITLE: Exploring The Structure of Young Disks

Abstract:
Disks around young stars are known to exhibit infrared variability. However, the physical mechanisms responsible for the observed variability are not yet fully understood. In this project we will detect changes in the structure of the disk, which is relevant to understanding how disks make planets. Many objects in the sample have holes in their disks, possibly formed by planets, and it would be interesting to see how their disk structure changes over time. Using data from infrared ground-based telescopes and the Spitzer Space Telescope, we will look for infrared variability of disks and try to explain the magnitude of the variability with changes in the disk's structure. The project will involve learning basic tools and techniques to analyze infrared data as well as comparing observations to theoretical models.

INTERN: Ryan McKinnon (Yale University)

ADVISOR: Prof. Alicia Soderberg (OIR Division)

PROJECT TITLE: The Ultra-Luminous Pan-STARRS Supernova PS1-11vo

Abstract:
Over the past few years, the field of time domain astronomy has exploded thanks to improvements in technology and instrumentation. The Pan-STARRS optical transient survey has uncovered a diversity in supernovae that has never yet been probed by previous surveys. In particular, the deep sensitivity of Pan-STARRS has enabled rare explosions with extraordinary luminosities to be discovered in rates higher than ever before. Here we report on the analysis of the Type IIn supernova, PS1-11vo, one of the longest lived and most luminous supernova explosions ever documented.

INTERN: Lia Medeiros (University of California - Berkeley)

ADVISOR: Dr. Aneta Siemiginowska (HEA Division)
CO-ADVISOR/MENTOR: Dr. Malgorzata Sobolewska (HEA Division)

PROJECT TITLE: X-ray Emission in Luminous Quasars

Abstract:
This project concerns a sample of quasars observed in the optical and X-ray bands. It will involve a compilation of the spectral energy distributions (SED) for the quasars using SDSS and Chandra (and other if appropriate) archival data and a self-consistent modeling of these data. The "accretion disk + hot corona" emission models have been developed by our group and we will apply them to the quasars in the sample using Sherpa, which is a modern modeling and fitting package in Python. Our sample contains high luminosity quasars with measured black hole masses with high accretion rates. The main goal of this project is to understand the accretion power and a contribution to the X-ray emission given by the hot corona.

INTERN: Becky Nevin (Whitman College)

ADVISOR: Dr. Francesca Civano (HEA Division)
CO-ADVISOR/MENTOR: Dr. Andrew Goulding (HEA Division)

PROJECT TITLE: Looking for recoiling SMBHs in Imaging survey

Abstract:
The existence of quasars misplaced with respect to their host galaxy center has been predicted by models of galaxy formation. When two galaxy merge, also their supermassive black holes (SMBHs) inside will merge. Depending on the initial conditions, the newly formed SMBH can recoil with respect to the center of the host galaxy, due to the asymmetric emission of gravitational waves. If the kick velocity is large enough, it will be possible to observe a misplaced quasar. The search of these objects have been really limited and only 6 candidates have been discovered so far.

I propose to search for misplaced quasars with respect to their host galaxies using imaging data. We will be using the GALFIT software for imaging analysis Galfit and we will look for galaxies showing asymmetries and irregular structures possibly due to a recent merging episode. Then, possible candidates will be studied in detail.

INTERN: Kayla Redmond (University of North Carolina at Asheville)

ADVISOR: Dr. Helen Kirk (RG Division)
CO-ADVISOR: Dr. Stella Offner (TA Division)

PROJECT TITLE: Mass Segregation in Dense Cores of Simulated and Observed Molecular Clouds

Abstract:
Background:
Within our close galactic neighborhood (a few hundred parsecs or lightyears), many molecular clouds have been detected where star formation is ongoing. Many puzzles remain in understanding star formation, including the influence of the large-scale cloud properties on the formation and evolution of the embedded forming stars. To better understand these processes, large surveys are underway at several telescopes focussing on nearby molecular clouds, and an unprecedented amount of data is becoming available. One of the precursors to these multi-telescope, multi-cloud surveys was COMPLETE (led by Dr. Goodman, [1]), which focussed on star formation in several molecular clouds, particularly the Perseus molecular cloud. Most stars appear to form in clusters, where interactions between dense star-forming cores may play an important role in subsequent evolution. Observations from the COMPLETE survey have shown that dense cores in Perseus tend to have very small motions relative to their immediate surroundings, and that the motions between cores within a clustered region are a factor of two smaller then the large-scale gas motions [2]. Interpretation of these results is challenging without knowledge of the 3D structure and dynamics of the cloud.

Project:
There is currently much debate over whether clusters found in star forming regions are born mass-segregated, or if the segregation is a result of dynamic evolution over in the first few million years. The student will examine this question with numerical simulations of star-formation, where the intial environmental conditions and the 3D cloud structure is known.

[1] Ridge, N. et al., "The COMPLETE Survey of Star Forming Regions: Phase 1 Data", 2006, AJ, 131, 2921
[2] Kirk, H., Pineda, J., Johnstone, D., & Goodman, A. "The Dynamics of Dense Cores in the Perseus Molecular Cloud. II. The Relationship Between Dense Cores and the Cloud," 2010, ApJ, 723, 457

INTERN: Bryan Terrazas (Columbia University)

ADVISOR: Dr. Paul Nulsen (HEA Division)

PROJECT TITLE: Particle Leakage and Aging of Radio Lobes

Abstract:
An extragalactic radio source is formed when a "supermassive" black hole at the center of a galaxy spews enormous amounts of energy into its surroundings through a pair of narrow, opposed jets. The jets inflate lobes with relativistic electrons and magnetic field. We see the radio source because relativistic electrons in a magnetic field produce synchrotron radiation.

Energy released in these outbursts can heat surrounding gas enough to affect the amount of gas supplied to the black hole, which creates a feedback loop linking the rate of gas cooling to the rate and size of outbursts. By limiting gas cooling, this "AGN feedback" can also limit star formation and there is mounting evidence that this is why the most luminous galaxies are not nearly as bright as predicted by simple galaxy formation models. As a result, there is great interest in understanding how radio sources work in detail.

In addition to the relativistic electrons and magnetic field, radio lobes probably contain other relativistic particles (cosmic rays) and thermal material that are largely undetectable. We want to relate the composition of radio lobes to their observable properties in order to study AGN feedback. The aim of this project is to investigate how the composition of radio lobes changes with time. By making a model for the aging of radio lobes, we hope to be able to use their radio properties alone to estimate key properties like their ages and how much energy was required to produce them.

The aims of the project will be to make models for aging radio lobes and to see if they can explain the X-ray and radio properties of a sample of observed radio sources. The project will involve both theory and data analysis, depending on the interests of the student.

INTERN: Nancy Thomas (University of Washington)

ADVISOR: Dr. Joe Hora (OIR Division)

PROJECT TITLE: Variability of Massive Young Stellar Objects

Abstract:
Young Stellar Objects (YSOs) are stars in the process of formation. They are surrounded by disks and are actively accreting material onto their surface. The disks also provide the material from which planets will form around these stars. Several recent investigations have shown a high rate of photometric variability in YSOs at near- and mid-infrared wavelengths. Theoretical models for the formation of stars remain highly idealized, and little is known about the mechanisms that produce the variability. There are many possible scenarios, such as rotation of the star and disk where hot spots are present, variability of accretion rates, and changes in the temperature of hot spots.

Even less is known about the variability of massive YSOs, which form under different conditions than most of the nearby low-mass stars. We have an ongoing Spitzer Space Telescope program to study massive star formation in the Cygnus-X region. We were recently awarded additional Spitzer time to monitor two fields in Cygnus-X to find the YSOs and characterize their variability. In conjunction with the Spitzer observations, over the past couple years we have conducted a ground-based near-infrared observing program of these fields using PAIRITEL, the automated infrared telescope at the Whipple Observatory. The near-IR and Spitzer observations will allow us to distinguish between different models to explain the origin of the variability. The summer project will involve extracting the near-IR photometry from the PAIRITEL images using a data reduction pipeline that we have developed at SAO, assembling the time-series data for each YSO in the field from the individual epochs, and correlating the data with the existing Spitzer observations. We will then characterize the variability of each of the YSOs, and determine periods and other properties of the variability which will help constrain models of star and planet formation.

## 2011 Interns

INTERN: Kate Alexander (Brown University)

ADVISOR: Prof. Alicia Soderberg (OIR Division)
CO-ADVISOR: Dr. Laura Chomiuk (OIR Division)

PROJECT TITLE: A Blind Search for Radio Transients in M51 and Associated Radio Observations of SN1994I

Abstract:
The student will conduct a search for radio transients in M51 using archival data from the Very Large Array collected over a period of six months following the discovery of the Type I supernova 1994I on May 2, 1994. The student will also construct light curves and analyse spectra for the supernova 1994I for the three available epochs, April 10, May 4, and August 8, 1994, and will use these data to study the physical properties of the supernova explosion and model the nature of the progenitor.

INTERN: Joanna Barnes (St. Andrews University)

ADVISOR: Dr. Rosanne DiStefano (TA Division)
CO-ADVISOR: Dr. Joshua Carter (OIR Division)

PROJECT TITLE: Gravitational Lensing Events

Abstract:
The study of nearby lenses is a relatively new endeavor and there are a variety of projects, both theoretical and observational, that can be productive on short time scales. The project I propose for this summer would provide training on both the theoretical aspects and observational aspects of searching for evidence of nearby lenses. The student would learn to compute both the astrometric and photometric shifts induced by gravitational lensing. She would then compare the results with what is and/or can be observed by a variety of telescopes, from those used by amateurs, to the Hubble Space Telescope. Very likely, the student will co-author one or more papers within the year after completing the summer program.

INTERN: Emily Cunningham (Haverford College)

ADVISOR: Dr. Francesca Civano (HEA Division)
CO-ADVISOR: Dr. Tom Aldcroft (HEA Division)

PROJECT TITLE: Properties of X-ray Emitting Quasar Close Pairs from the Chandra COSMOS Survey

Abstract:
Pairs of X-ray emitting sources within a small range of redshift and at a distance of 10-20kpc one to the other have been found in the Chandra COSMOS survey. Galaxy evolution theory says their host galaxies are likely to merge, and that their activity may be stimulated by tidal disruptions of their ISM. Questions we wish to address include: Does being in a pair, on a 'death plunge' affect the quasars, or are they unaware of the fate that is in store? Do their optical spectra look any different from normal quasars? Do their X-ray to radio spectral energy distributions look peculiar or normal? Do these quasar pairs lie in an unusual place on any diagnostic diagrams, i.e. the mass (M) versus luminosity (L) plane or optical vs near-IR slope?

We have reduced optical and X-ray data on ~15 such quasar pairs from the COSMOS survey. The student will measure X-ray and optical spectra of this sample of quasar pairs, extract SEDs, measure quasar mass, luminosity, optical slope and NIR slopes, and put these pairs on diagnostic diagrams such as Mass versus Luminosity or optical versus near-IR slope. These results will then be compared with simulations to estimate the significance of their numbers relative to what is predicted from standard clustering models.

INTERN: Chelsea Harris (UC Santa Barbara)

ADVISOR: Dr. Stella Offner (TA Division)
CO-ADVISOR:Dr. Helen Kirk (RG Division)

PROJECT TITLE: Dynamics of Dense Cores in Simulated and Observed Molecular Clouds

Abstract:
Background:
Within our close galactic neighborhood (a few hundred parsecs or lightyears), many molecular clouds have been detected where star formation is ongoing. Many puzzles remain in understanding star formation, including the influence of the large-scale cloud properties on the formation and evolution of the embedded forming stars. To better understand these processes, large surveys are underway at several telescopes focussing on nearby molecular clouds, and an unprecedented amount of data is becoming available. One of the precursors to these multi-telescope, multi-cloud surveys was COMPLETE (led by Dr. Goodman, [1]), which focussed on star formation in several molecular clouds, particularly the Perseus molecular cloud. Most stars appear to form in clusters, where interactions between dense star-forming cores may play an important role in subsequent evolution. Observations from the COMPLETE survey have shown that dense cores in Perseus tend to have very small motions relative to their immediate surroundings, and that the motions between cores within a clustered region are a factor of two smaller then the large-scale gas motions [2]. Interpretation of these results is challenging without knowledge of the 3D structure and dynamics of the cloud. The most promising avenue to improving understanding is through comparisons with numerical simulations of star-formation, where the intial environmental conditions and the 3D cloud structure is known.

Project:
In this project, the student will create and analyze synthetic observations of simulated high-resolution turbulent molecular clouds [3]. The student will use existing code to derive the observed velocity distribution of various molecules, like N2H+ and 13CO, and obtain measurements in a manner that mimics real observing modes. Comparisons between the observed' and real 3D dynamical properties will provide insight into how the actual observational data can be interpreted. Comparisons can also help to constrain the important physics and initial conditions used

[1] Ridge, N. et al., "The COMPLETE Survey of Star Forming Regions: Phase 1 Data", 2006, AJ, 131, 2921 [2] Kirk, H., Pineda, J., Johnstone, D., & Goodman, A. "The Dynamics of Dense Cores in the Perseus Molecular Cloud. II. The Relationship Between Dense Cores and the Cloud," 2010, ApJ, 723, 457 [3] Offner, S., Klein, R., & McKee, C. "Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to

INTERN: John Hoffman (University of Illinois)

ADVISOR: Dr. Hans Moritz Guenter (HEA Division)
CO-ADVISOR: Dr. Nick Wright (HEA Division)

PROJECT TITLE: Stellar Cycles

Abstract:
Our sun has a well-known activity cycle of 11 years. Activity can be traced in cromospheric signatures like Ca H and K and traditionally this has been the way to search for cycles on other stars as well (the famous Mount Wilson S index), however on our sun the difference between minimum and maximum activity is much stronger in X-rays than in the Chromosphere. Only very few stars have observed cyclic variability in X-rays and only in one case (our sun) actually more than one cycle is observed. Individual stars, which are monitored on a long-term basis are e.g. alpha Cen and 61 Cyg.

Project:
XMM-Newton and Chandra have been launched more than a decade ago and there are plenty of fields in the archive, which have been observed for several times for varying reasons. Nick has looked at the stellar content of the COSMOS field and in this project the student would analyse archival data. It it a well-defined and self-contained project, which leads the student through the analysis of X-ray data from selecting the data in the archive, downloading it, reduce it, detect point sources, measure count rates (and compare his/her results with pipeline products), extract and fit spectra (to confirm it is a star - this goes beyond pipeline products), generate long-term lightcurves and search for periodicities.

We will start with XMM-Newton observations of the spectroscopic cal targets and look for the stars in the field of the MOS and PN fields, because these fields have been visited a large number of times. Depending on the progress the project makes we can easily extend it (we have a list of sky regions XMM has looked at more then 10 times and we also had a first look at some of the repreated Chandra observations, e.g. the stars in the Deep Field South).

If we find stellar cycles, this will result in the publication, if not, we will try to estimate and upper limit and the magnitude and length of average stellar cycles.

INTERN: Mackenzie Jones (Butler University)

CO-ADVISOR: Dr. Joshua Carter (OIR Division)

PROJECT TITLE: The Complete Life-Cycle of an Exoplanet Transit Light Curve

Abstract:
I have a stockpile of a dozen or more good-quality transit light curves from several exoplanets, which I would really like to fully reduce and fit (and, ideally, publish). The student would get to see the entire life cycle of a transit light curve: photometry to get the best light curve, literature search for other light curves of the same planet, joint fits of all the light curves to get a consistent set of orbital parameters, examining the timing and other parameters, and then writing up the results. Most of the transits were observed with a new PI instrument on the IRTF, and I have five transits scheduled to be remotely observed with the same instrument between early June and late July; it would be great if the intern could help me with those observations.

INTERN: Ali Ahmad Khostovan (UC Irvine)

ADVISOR: Dr. Jan Forbrich (HEA Division)
CO-ADVISOR: Drs. Charlie Lada, Karin Oberg (RG Division)

PROJECT TITLE: Initial Conditions of Star Formation in the Pipe Nebula

Abstract:
Stars in the mass range of our own Sun form in molecular cloud cores. Starless cores thus are ideal laboratories for the initial conditions of low-mass star formation. The best tool to study these cold cloud cores (with temperatures of ~10 K) are observations in molecular transition lines that occur in the millimeter wavelength (microwave) radio range.

The Pipe Nebula is a nearby molecular cloud complex with an unusually low star formation rate. The region contains hundreds of starless cores and only a single cluster of young stars. The starless cores have been identified by observations of how the Pipe Nebula affects background starlight (extinction mapping). We have surveyed the entire region extensively with various observational techniques, and we have obtained observations of ten different molecular transition lines toward the sample of starless cores using single-dish radio telescopes in North America and Australia. Early results suggest that cores with similar properties (e.g. mass, radius, density, stability, etc.) show very different molecular line emission, and the underlying chemical differences are likely related to their relative evolutionary stages. While most of the chemistry in dense cores occurs in the gas phase, the surfaces of dust grains are involved as well. The millimeter radio observations will thus allow us to study chemical differences across the sample that will shed new light on the question why the Pipe Nebula region has but one region of active star formation. In addition to the pointed observations of starless cores, we also have data to a analyze the spatial structure of selected cores, for example from molecular line mapping observations. This project will start with a survey of the literature concerning the chemistry of starless cores. In a second step the results will be applied to the Pipe Nebula observations, beginning with a cross-correlation of the molecular line detections and other properties of the cores.

INTERN: Sajjan Mehta (Drexel University)

ADVISOR: Dr. Scott W. Randall (HEA Division)
CO-ADVISOR: Dr. Paul Nulsen (HEA Division)

PROJECT TITLE: X-ray Properties of the Intra-Cluster Medium in Optically Selected Galaxy Groups

Abstract:
As the largest virialized structures in the Universe, clusters of galaxies are extremely useful probes of cosmology. Since galaxy clusters are filled with diffuse, high temperature gas that shines brightly at X-ray wavelengths (the intracluster medium, or ICM), X-ray observations are particularly well suited to the detection and study of clusters. If one is to use X-ray observations to catalog the properties of galaxy clusters, it is important to understand the physics of the ICM. Galaxy groups, the lower-mass cousins of galaxy clusters, are ideal for the study of physical processes in the ICM since there are more of them nearby, and since such processes will have a larger relative impact on the ICM in groups due to their shallower gravitational potentials. Furthermore, although groups are less massive than clusters, they are more numerous, and contain a significantly larger fraction of the total mass in the Universe as compared to clusters. They are therefore interesting objects to study

One concern when dealing with X-ray selected samples of galaxy clusters or groups is the inherent selection bias in such samples. X-ray brighter objects will be preferentially detected over fainter ones, leading to an over-representation of such objects in samples. Thus, X-ray selected samples may not be a fair representation of the full population of groups and clusters. With this project, we will examine the X-ray properties of an optically selected sample of galaxy groups. Although optically selected samples will have their own selection biases, these biases are expected to be different from, and largely independent of, X-ray selection biases. A difference between the X-ray properties of X-ray selected and optically selected group samples would indicate significant selection biases, which would need to be fully understood to properly interpret our samples. In particular, we will search for a bimodal distribution in the central entropy of optically selected groups, which is observed cluster samples. Groups with higher central entropy may be overlooked in X-ray selected group samples, since they are expected to be less X-ray bright than low central entropy groups (as is observed with clusters).

The student will learn the fundamentals of high energy astrophysics in the context of the study of galaxy groups and clusters, and the basics of analyzing X-ray data from working with archival Chandra observations. The work will involve understanding, running, and possibly modifying some "homemade" code to carry out the analysis. Some coding experience, particularly a familiarity with Perl, is a plus (although not required).

INTERN: Alex Spatzier (Oberlin College)

ADVISOR: Dr. Catherine Espaillat (RG Division)
CO-ADVISOR: Dr. Scott Wolk (HEA Division)

PROJECT TITLE: A Multi-Wavelength View at a Stellar Nursery

Abstract:
Stars similar to our Sun form deeply embedded in molecular clouds. As they evolve, they become less and less embedded, and they form circumstellar disks, the birthplace of planets. The processes of low- mass star formation can be best studied by observations of nearby young clusters. IC 348 is such a nearby cluster of young stars that lies at a distance of only about 300 pc (1000 light years) from the Sun. To characterize the population of this cluster, astronomers use observations at very different wavelengths. It has become a common tool to use both infrared and X-ray data to assemble a census of young stars in different evolutionary stages. We have recently obtained new X-ray images of this cluster with the Chandra X-ray Observatory, improving both on the sensitivity and the spatial coverage of previous datasets. These images will allow us to find previously undetected X-ray sources and better characterize the population of this cluster. The new X-ray sources that we will find can then be characterized by existing infrared, centimeter radio, and submillimeter observations. The infrared data, both from ground-based telescopes and the Spitzer Space Telescope, will tell us about the evolutionary stage of the sources by providing information on the existence of circumstellar disks. We will use the submillimeter data, obtained at longer wavelengths than the far infrared, to characterize the youngest sources that are still deeply embedded in their natal cloud cores. Finally, radio data at centimeter wavelengths can help us to further constrain the high-energy processes that are related to the X-ray emission.

INTERN: Jordan Wheeler (University of Missouri - Columbia)

ADVISOR: Dr. Huiqun Wang (AMP Division)
CO-ADVISOR: Dr. Sarah Stewart (EPS Department, Harvard University)

PROJECT TITLE: Martian Weather Observations Using Mars REconnaissance Orbiter (MRO) Data

Abstract:
This project consists of making Mars Daily Global Maps from images taken by the MRO Spacecraft and using them to study the pattern of Martian weather. MRO Mars Color Imager takes 13 sets of multispectral global map swaths each day. These images will be radiometrically and photometrically corrected, projected and merged into a global weather map each day. Dust storms and clouds will be identified, recorded and classified. Patterns of dust storms and clouds of various types will be summarized. If there is still time left, then the results above can be compared to atmospheric eddies derived from the concurrent temperature data and modeled by a Mars General Circulation Model. Student working on this project will practice IDL image processing of spacecraft data, gain expert knowledge of Martian weather, and apply atmospheric science principles to another planet.

## 2010 Interns

INTERN: Justin Brown (Franklin and Marshall College)

ADVISOR: Dr. Mukremin Kilic (SSP Division)
CO-ADVISOR: Dr. Warren R. Brown (OIR Division)

PROJECT TITLE: Testing Stellar Evolution Theory with Low-mass White Dwarfs

Abstract:
The Galaxy is not old enough to produce low mass (M < 0.45 solar masses) white dwarfs through single-star evolution. Thus known low mass white dwarfs are thought to be helium-core white dwarfs formed in binary systems in which a companion strips the outer envelope of the evolving star before it ignites helium in its core. An alternative, however, is that metal rich stars may lose too much mass on the red giant branch (due to larger opacity in their atmospheres) and do not ignite helium burning, thereby forming helium-core white dwarfs. Thus the binary fraction of low mass white dwarfs provides a sensitive test of stellar evolution and mass loss on the red giant branch.

Our goal is to measure the binary fraction of white dwarfs as a function of mass, and test for the signature of He-core white dwarfs evolved from metal rich single stars. We already obtained optical spectroscopy of two dozen white dwarfs using the FAST instrument for the past two years. The intern will reduce these data using simple IRAF routines and derive radial velocities. Based on these radial velocity measurements, and optical and near-infrared photometry, we will evaluate the fraction of single low-mass white dwarfs as a function of mass. Finding a He-core white dwarf without a binary companion is a strong test of stellar evolution, with implications for mass loss on the red giant branch and the production of Type Ia supernovae.

INTERN: Jared Coughlin (Villanova University)

ADVISOR: Dr. Darin Ragozzine (TA Division)
CO-ADVISOR: Dr. Matthew J. Holman (TA Division)

PROJECT TITLE: Transneptunian objects

Abstract:
Exoplanet mutual events are when two extra-solar planets cross in front of one another as seen from Earth. Similar events occasionally occur in other contexts, such as solar system mutual events. Transiting exoplanets themselves are a type of mutual event between a planet and its host star. Throughout astrophysics, mutual events encode significant amounts of unique information that often cannot be determined in any other way. Even though mutual events between two exoplanets have not been previously considered in any detail, they potentially offer an exciting amount of interesting science that would otherwise not be possible. This project will expand preliminary investigations already underway and will look at larger ensembles of simulated planetary systems to examine in more detail the type and frequency of exoplanet mutual events that could be observed by the Kepler Space Telescope and/or the James Webb Space Telescope. The main goal of the project is to determine the basic properties of these events:

How probable is it that exoplanetary systems have the appropriate alignment (with respect to Earth) to see mutual events?
When mutual events do occur, how frequent are they?
What is the typical duration and expected light curve amplitude of various events, especially the most frequent ones?
What information is needed to accurately predict mutual events in advance?
What orbital and physical properties can be determined from realistic observations of these events?

This observationally-motivated theoretical study will bring exoplanet mutual events to the fore as a potential tool for studying planetary systems beyond on own.

INTERN: Jason Kong (University of California at Berkeley)

ADVISOR: Dr. Paul E. J. Nulsen (HEA Division)
CO-ADVISOR: Dr. Ralph P. Kraft (HEA Division)

PROJECT TITLE: Composition of Radio Lobes

Abstract:
An extragalactic radio source is formed when a "supermassive" black hole at the center of a galaxy spews enormous amounts of energy into its surroundings through a pair of narrow, opposed jets. The jets inflate lobes with relativistic electrons and magnetic field. We see the radio source because relativistic electrons in a magnetic field emit synchrotron radiation.

Energy released in these outbursts can heat surrounding gas enough to affect the supply of gas to the black hole, which creates a feedback loop that links the rate of gas cooling to the rate and size of outbursts. By limiting gas cooling, this "AGN feedback" can also regulate the rate of star formation and there is mounting evidence that this is what holds the rate of star formation in massive galaxies to a trickle, in effect setting the brightness of the most luminous galaxies. As a result, there is great interest in understanding how radio sources work in detail.

In addition to the relativistic electrons and magnetic field, radio lobes probably contain other relativistic particles (cosmic rays) and thermal material that are largely undetectable. We need to be be able to relate the composition of radio lobes to their observable properties in order to study AGN feedback. The aim of this project is to investigate the composition of the radio lobes of one of the nearest extragalactic radio sources, Fornax A.

The radio spectrum constrains the strength of the magnetic field and the number of relativistic electrons, but additional information is required to determine these separately. Relativistic electrons scatter microwave background photons into the X-ray band. Detecting this "inverse Compton" emission provides an independent constraint. However, non-uniformities in the radio and X-ray emission raise theoretical challenges for the simple models that have been employed to interpret such data. X-ray and radio data will be used to study the radio source Fornax A. The project will involve both data analysis and theory, depending on the interests of the student.

INTERN: Sam McCandlish (Brandeis University)

ADVISOR: Dr. Rosanne DiStefano (TA Division)
CO-ADVISOR: Dr. Hagai Perets (TA Division)

PROJECT TITLE: The Prediction of Gravitational Lensing Events

Abstract:
When monitoring programs designed to discover gravitational lensing events began, it was assumed that the lenses would be located several kpc from Earth. Theoretical work shows, however, that nearby lenses (within roughly a kpc) contribute significantly to the rate. Observations are now beginning to confirm this. The project we plan for this summer is designed to take the study of nearby lenses an important step farther, by developing methods to predict future events. We will use theory and archived data to work out the optimal methods with which to carry out this new enterprise. We will follow up on specific nearby systems that may be first for which lensing events are predicted and then detected.

INTERN: Elisabeth Otto (Ohio State University)

ADVISOR: Dr. Paul J. Green (HEA Division)
CO-ADVISOR: Dr. Anna Luise Frebel (OIR Division)

PROJECT TITLE: Stalking the Elusive Dwarf S Star

Abstract:
Stars with C/O close to or above unity (S and C stars, respectively) are normally thought to all be giants, since only thermal pulses on the asymptotic giant branch can dredge up carbon. But mass transfer in a binary system can chemically imprint a (lower mass) companion's atmosphere even after the (higher mass) AGB star has faded to a white dwarf. Dwarf Carbon (dC) stars, created through the same process, are now known to be more common by far than giants. So where are the S dwarfs? Constraints on the S dwarf fraction would place useful limits on the intensity and duration of binary mass transfer episodes. Yet none have ever been found. We have obtained FAST spectra of a sample of 56 known S giants. We will prepare and publish the the first digital spectral atlas of S giants. We will then use synthetic SDSS colors and proper motions to find S dwarfs from the SDSS.

INTERN: Dominiqe Segura-Cox (University of Michigan)

ADVISOR: Dr. Joseph L. Hora (OIR Division)

PROJECT TITLE: Star Formation in the Massive Cygnus-X Complex

Abstract:
The Cygnus-X region is one of the brightest regions of the sky at all wavelengths and one of the richest known regions of star formation of the Galaxy. It contains as many as 800 distinct HII regions, a number of Wolf-Rayet and OIII stars and several OB associations. Cygnus-X also contains one of the most massive molecular complexes of the nearby Galaxy, significantly larger than other nearby molecular clouds with OB associations such as Orion A, M17, or Carina.

We are conducting a Spitzer Legacy survey of the Cygnus-X complex, with the following goals: 1) to analyze the evolution of high mass protostars with a large and statistically robust sample at a single, known distance, 2) study the role of clustering and triggering in high mass star formation, 3) study low mass star formation in a massive molecular cloud complex dominated by the energetics of ~100 O-stars, and 4) determine what fraction of all young low mass stars in the nearest 2 kpc are forming in this one massive complex. The data have been obtained during the past couple years, preliminary catalogs and mosaics have been completed, and candidate young stellar objects (YSOs) have been identified.

Before the cryogen was exhausted on Spitzer, we obtained IRS spectra of a sample of ~20 massive YSOs. The spectra of the objects provide key data, along with the rest of the objects Spectral Enery Distribution (SED), to determine the characteristics of the object, including the physical parameters and evolutionary state. An initial characterization can be done by fitting the spectra and SEDs with the grid of precomputed models by Robitaille et al. (2007). More detailed modeling of the individual sources can be done depending on the spectral information in the IRS data. For example, if [Ne II] and [S IV] are detected, these lines can be used to estimate the exciting stars temperature. The continuum emission and silicate absorption depth can provide constraints to fit models that will allow us to estimate the masses of the gas and dust, the column densities of the absorbing material, and the luminosities of the objects. The project would consist of completing the reduction of the spectra and performing an analysis of the massive YSOs.

INTERN: Brian Svoboda (Western Washington University)

ADVISOR: Dr. Karin Oberg (RG Division)

PROJECT TITLE: Origins of chemical complexity during (exo-)planet formation

Abstract:
Chemistry plays an important role in the structure and evolution of the disks around young stars where planets form, with implications for the composition of comets and planets both in our Solar System and in the increasing number of extrasolar systems. Especially interesting are detections of small organic molecules in disks around Sun-like stars, which bear on the origins of life. The aim of this project is to constrain how and where in the disk these small organic molecules form, using recently acquired observations of gas-phase formaldehyde (H2CO) in such disks from the Submillimeter Array (SMA). The first part of the project will be to use the SMA data directly to constrain the spatial extent of H2CO in disks and to compare its distribution and average temperature with observations of other, better understood, molecules. This part will involve analysis of interferometry spectral data using Miriad and IDL. The second part of the project will be to address the origins. Current models of the chemistry in disks underestimate the H2CO abundances by orders of magnitude. These models only include gas phase chemistry, however, and laboratory experiments suggest that H2CO can also form on icy dust grains -- the building blocks of comets and planets. This process will be investigated by modifying an existing modeling code to include this surface formation pathway as well as different pathways to evaporate the H2CO into the gas phase. The model results will be compared with the SMA observations using a radiative transfer code. We expect this project will advance the overall understanding of the chemical evolution in disks, in particular the role of grain surfaces for the formation of organic species.

INTERN: Kimberly Ward-Duong (Northern Arizona University)

ADVISOR: Dr. Scott W. Randall (HEA Division)
CO-ADVISOR: Dr. Marie Machacek (HEA Division)

PROJECT TITLE: Mergers, Feedback, and the IntraCluster Medium

Abstract:
One of the most important questions facing models of galaxy evolution today is how central supermassive black holes, found in most galaxies, co-evolve with their host galaxies. A key element to this puzzle is understanding the dynamical connections between galaxy interactions in galaxy groups and clusters, the feedback cycle from active galactic nuclei (AGNs), and black hole fueling and growth. Signatures of these interactions are imprinted on the hot X-ray emitting gas in the form of edges (cold fronts or shocks), stripped tails, outflows, cavities and buoyant bubbles, or other asymmetric features. Measurements of temperatures and densities in these features allow us to constrain 3-dimensional velocities, orbits, and the interaction history of the galaxies, as well as the flow of matter and energy from the AGN and the host galaxy into the surrounding gas.

AS0851: The mass of a galaxy's central black hole is known to be strongly correlated with the properties of the host galaxy's central stellar velocity dispersion (sigma) and with the host galaxy's stellar bulge mass (or K-band luminosity). NGC6861 in AS0851 has one of the highest central stellar velocity dispersions measured for any elliptical galaxy, similar to that of M87 the dominant galaxy in the massive Virgo galaxy cluster, yet NGC6861 is only the second brightest galaxy in only a moderately massive galaxy group. The mass of the central black hole inferred from the black hole mass - sigma relation is ~2 billion solar masses, almost an order of magnitude greater than the black hole mass inferred from the mass of NGC6861's stellar bulge. The question is why, and which, if either, correlation correctly predicts NGC6861's black hole mass? The answer must lie in the interaction and AGN feedback history of the two dominant galaxies, NGC6868 and NGC6861. We have identified preliminary features of interest in a previous study of this system (Machacek et al. 2010, ApJ, 711, 1316), but the data were too sparse for a complete analysis. We have recently obtained a total of >100 ks of Chandra data on each dominant galaxy, NGC6868 and NGC6861. In this project the student will learn to use standard X-ray imaging and analyis tools (ds9, CIAO, FTOOLS, XSPEC) as well as specialized scripts to construct images and temperature maps from combined Chandra data on these galaxies to identify X-ray bridges, hot spots, edges, tails and other features of interest. The student will use these analyses to determine the thermodynamic properties of the diffuse gas and origin of observed wakes and tails, measure galaxy and gas velocities, model galaxy orbits and interaction history of NGC6861 and NGC6868, and constrain the mass of NGC6861's black hole.

INTERN: Sarah Wellons (Princeton University)

ADVISOR: Dr. Alicia M. Soderberg (TA Division)

PROJECT TITLE: A Detailed Study of the Host Galaxies of Type Ib Supernovae

Abstract:
We will test whether metallicity is the key parameter that enables some Type Ibc supernova progenitors to produce gamma-ray bursts while most cannot. Unfortunately we can't measure the metallicity of the dying star after the explosion. However, low metallicity stars are likely to be found in low metallicity galaxies. Therefore, by studying the properties of the host galaxies of Type Ibc supernovae we can learn about the properties of the progenitors. The student will analyze a sample of spectra for two dozen Type Ibc supernovae and extract the metallicity and star-formation rates. Through comparison with models, we will extract information about the stellar population in each host galaxy. These diagostics will be compared with the properties of gamma-ray burst host galaxies as compiled from the literature. Through this effort we will shed light on whether gamma-ray burst progenitor stars are lower metallicity than those of ordinary supernovae.

INTERN: Schuyler Wolff (Western Kentucky University)

ADVISOR: Dr. Ruth Murray-Clay (TA Division)

PROJECT TITLE: Resonance capture in planetary systems

Abstract:
As planets migrate through the disks from which they were born, they can capture other bodies into mean motion resonances. In these special dynamical configurations, the two bodies orbit their host stars with periods dynamical configurations, the two bodies orbit their host stars with periods that form an integer ratio. This phenomenon occurs in the solar system, where Pluto and more than 100 other Kuiper belt objects are known to be in resonance with Neptune. For example, Pluto orbits twice for every three orbits of Neptune, and this configuration protects Pluto from close encounters with Neptune that would otherwise eject it from the solar system. Extrasolar planetary systems in which two planets are in resonance have also been observed, presumably also resulting from capture during migration.

Standard theories of resonance capture assume that the planet starts on a roughly circular orbit. In the outer solar system, it has been suggested that Neptune may have had a substantial eccentricity at the beginning of its migration, which was damped as migration proceeded. Studies of extrasolar systems in resonance suggest that for observed systems to form, substantial eccentricity damping must have occurred during migration. In this summer project, the student will use N-body simulations to investigate the differences in resonance capture resulting from eccentricity damping. He or she will apply the results either to resonance structure in the Kuiper belt in anticipation of an unbiased census of orbits from Pan-STARRS, or to exoplanet systems in anticipation of direct imaging surveys which may yield many resonant systems. The student will learn how to use a standard N-body integrator and how to plot with IDL.

A course covering Hamiltonian dynamics would be useful background. I will attend a conference in Philadelphia on the Trans-Neptunian region of our solar system during the week of June 28. I have money available to bring the REU student with me if he or she is interested. Dynamics of the small objects in the solar system informs much of our understanding of dynamics as applied to extrasolar systems, so this would be appropriate regardless of which project the student wishes to do.

## 2009 Interns

List of colloquium talks given during the summer of 2009
Program of the SAO Summer Intern Symposium, August 12, 2009
2009 Summer Program Calendars for June July , and August
Abstracts for posters presented at the January, 2010 AAS meeting

INTERN: Ingrid Beerer (UC Berkeley)

ADVISOR: Dr. Joe Hora (OIR Division)

PROJECT TITLE: Analyzing Optical Spectra of Massive Stars and Young Stellar Objects in Cygnus-X

Abstract:
The Cygnus-X region is one of the brightest regions of the sky at all wavelengths and one of the richest known regions of star formation of the Galaxy. It contains as many as 800 distinct HII regions, a number of Wolf-Rayet and OIII stars and several OB associations. Cygnus-X also contains one of the most massive molecular complexes of the nearby Galaxy, significantly larger than other nearby molecular clouds with OB associations such as Orion A, M17, or Carina.

We are conducting a Spitzer Legacy survey of the Cygnus-X complex, with the following goals: 1) to analyze the evolution of high mass protostars with a large and statistically robust sample at a single, known distance, 2) study the role of clustering and triggering in high mass star formation, 3) sudy low mass star formation in a massive molecular cloud complex dominated by the energetics of ~100 O-stars, and 4) determine what fraction of all young low mass stars in the nearest 2 kpc are forming in this one massive complex. The data have been obtained during the past couple years, preliminary catalogs and mosaics have been completed, and candidate young stellar objects (YSOs) have been identified.

We obtained optical spectra using the FAST instrument during the fall of 2008 of two samples of objects in the 2x2 deg field near DR21 in Cygnus-X. First, we observed the YSO candidates that are sufficiently optically bright that have been identified by the IRAC and near-IR observations in the DR 21 field. In addition, we observed another sample of stars identified from optical surveys as being possible O or B type stars. Much of the Cygnus region has not been adequately surveyed to sufficiently characterize the population of the most massive stars that generate the majority of the UV flux in the region. To understand the effects of these massive stars on their environments and possible triggering of star formation in the surrounding clouds, we must have a census of the massive stars in the region. We obtained data on approximately 200 stars that fall in the color-magnitude region consistent with O or B-type stars. The summer project will involve using stellar classification software to analyze the FAST data to determine the stellar types of the candidate O and B stars, and to produce a catalog of the most massive stars in the DR21 neighborhood. The spectra of the YSO stars will also be analyzed, along with the IR photometry from the Spitzer Cygnus-X survey, to verify the classification of these objects as YSOs, and to determine the age and mass of the stars.

INTERN: Ian Czekala (University of Virginia)

ADVISOR: Dr. Sean Andrews

PROJECT TITLE: SMA and Spitzer Study of the Protoplanetary Disk around HD 98800

Abstract:
With the growing number of planets found orbiting Sun-like stars, there is increasing attention on the origins of our Solar System and others like it. Direct observations of the reservoirs of planet-building material- the disks around young stars - play a critical role in testing planet formation theories. This project will use data from the Smithsonian's Submillimeter Array (SMA), located on Mauna Kea, Hawaii, and the Spitzer Space Telescope, to characterize the physical conditions in the unique protoplanetary disk around the young multiple star system HD 98800. At an age of 5-10 Myr, this system probes a critical time period in the evolution of disk material and the potential birth of a planetary system. Moreover, the HD 98800 system is an interesting test case to explore how disks are affected by dynamical interactions with stellar companions. The student working on this project will learn the basic tools and techniques used to analyze millimeter interferometer data and infrared spectral energy distributions. He/she will also gain valuable experience comparing these data to theoretical models of protoplanetary disks and interpreting the results. If time permits, there are opportunities to extend the project to other disk targets. The project report should lead to journal publication.

INTERN: Maria Drout (University of Iowa)

ADVISOR: Dr. Alicia Soderberg

PROJECT TITLE: Diversity of Massive Stellar Explosions

Abstract:
Massive stars end their short lives in spectacular explosions that are visible to the far reaches of the Universe. These explosions give birth to extreme compact objects -- black holes and neutron stars -- and play a crucial role in galaxy evolution through the injection of metals and mechanical energy into their environments. Equally important, through the synthesis of new elements, massive stars help to fuel the formation of stars, planets, and ultimately life.

While our understanding of some basic aspects of stellar death date back several decades, recent findings are forcing us to fundamentally rethink the ways in which massive stars die. In the basic picture, the stellar core exhausts its nuclear fuel and collapses spherically to a neutron star or black hole, thereby generating a shockwave that explodes the star. About 99 percent of the explosion energy is expected to be emitted in neutrinos, with the remaining energy propelling several solar masses of ejecta to velocities of 10,000 km/s. The radioactive decay of freshly synthesized Nickel-56 gives rise to bright optical emission that peaks days to weeks after the explosion, the observed signpost for a new supernova.

This simple scenario, however, cannot explain the observed intimate connection between relativistic gamma-ray burst jets and spherical supernova explosions. To that end, I have designed a comprehensive observational program for an REU student to map the diversity of supernova properties and environments in comparison to those of gamma-ray bursts.

Project 1: An Optical Study of Type Ibc Supernovae and Comparison to Gamma-ray Burst Supernovae

Type Ibc supernovae represent the explosive death of the most massive stars in the Universe. They represent 10 percent of all local supernova discoveries. We now know that a small fraction of Type Ibc supernovae (less than 1 percent) also produce gamma-ray burst jets during the explosion. However, the burning question remains, why are only some supernovae able to produce gamma-ray bursts? Possibilities include the progenitor star properties: energy and/or metallicity.

Using optical data from the robotic Palomar 60-inch telescope for a sample of two dozen local Type Ibc supernovae, the student will perform photometry on the images and construct optical light-curves for each supernova. Since the light-curve is powered by the radioactive decay fo Nickel-56, the student will fit some simple analytic models to estimate the mass of Nickel synthesized in the explosion and compare to the light-curves for gamma-ray burst supernovae. Through this statistical comparison we will answer the question of whether gamma-ray burst supernovae are more energetic and hence synthesize a larger mass of Nickel. This very important result will result in a first author paper for the student by the end of the summer.

Project 2: A Detailed Study of the Host Galaxies of Type Ibc Supernovae

We will test whether metallicity is the key parameter that enables some Type Ibc supernova progenitors to produce gamma-ray bursts while most cannot. Unfortunately we can't measure the metallicity of the dying star after the explosion. However, low metallicity stars are likely to be found in low metallicity galaxies. Therefore, by studying the properties of the host galaxies of Type Ibc supernovae we can learn about the properties of the progenitors. The student will analyze a sample of spectra for two dozen Type Ibc supernovae and extract the metallicity and star-formation rates. Through comparison with models, we will extract information about the stellar population in each host galaxy. These diagostics will be compared with the properties of gamma-ray burst host galaxies as compiled from the literature. Through this effort we will shed light on whether gamma-ray burst progenitor stars are lower metallicity than those of ordinary supernovae. This is a longer term project but we aim to at least start it during the summer if the student is interested.

INTERN: Dan Gifford (University of Western Washington)

ADVISORS: Dr. Matt Ashby, Dr. Joe Hora

PROJECT TITLE: Deep Infrared Galaxy Counts

Abstract:
The student will analyze deep/faint galaxy counts at 3.6, 4.5, 5.8, and 8.0 microns in a uniquely deep Spitzer/IRAC survey field, the so-called IRAC Calibration Field (IRAC-CF). This field is the deepest IRAC survey field in existence in the four IRAC bands, and the deepest portion covers four times as much area as the next-deepest survey, GOODS Ultra-Deep. What's more, we anticipate an additional integration at 3.6 and 4.5 um this April that will be the equivalent of the total of all existing data to date. These data make it possible to measure the source counts in the IRAC bands at the very faintest levels, where they suffer heavily from confusion.

Hora and Ashby have already reduced and coadded the 100+ IRAC mosaics of the field. Instead of basic data crunching, the student will be asked to use SExtractor to generate the deepest-ever IRAC source count measurements, to address quantitatively the effects of source confusion in the field via simulations, and to interpret/compare the outcomes to an abundant literature on this topic. We will investigate the use of HST/ACS F814W counts as priors; we are also hoping to have available a deep MMT/MMIRS K-band image of the field that may prove more useful for this purpose by virtue of being a better match to the IRAC wavelengths.

INTERN: Derek Huelsman (University of Cincinnati)

ADVISORS: Dr. Massimo Marengo, Dr. Nancy Evans

PROJECT TITLE: The Mysterious Case of the Cepheid Missing Mass

Abstract:
Astronomers think that Cepheids are among the coolest stars. It all started exactly 100 years ago, at the Harvard College Observatory, when Henrietta Leavitt found one of the most widely used laws in astronomy. By monitoring the brightness variations of Cepheid stars, she discovered that the period of such variations was directly related to their average brightness. This relation, once properly calibrated, allows Cepheids to be used as powerful "standard candles", the first step in a sequence of distance indicators that we still use today to measure the size of the cosmo.

One would think that after 100 years of intense study, we should know everything there is to know about Cepheids. That is not so. There is a lingering mystery about their life, that even the most advanced observations and theoretical works have not yet been able to solve. This mystery concerns their mass. Whenever we have been able to directly measure the mass of Cepheid stars, we surprisingly found a number significantly smaller that the mass predicted by the most advanced models of stellar evolution. Take Polaris, the nearest Cepheid: its measured mass is as much as 10-15% smaller than the mass theoreticians can account for. Where has this missing mass gone?

One possibility is that this mass has been lost along the way, blown away by stellar winds as the star aged and entered the Cepheid phase (Cepheid stars are not born as variables, they become Cepheids once they reach their middle age). If that's what happened, then the evidence of such event may be found by searching for the ejected material still lurking in the neighborhood of these stars. The infrared Spitzer Space Telescope, thanks to its unchallenged sensitivity to the faint emission from the ghostly matter dispersed in the interstellar medium, is the perfect tool to investigate this hypothesis. To this aim, we have observed a sample of 29 nearby Cepheids with the Spitzer's InfraRed Array Camera (IRAC). In this dataset, we may find the missing clue to solve the long standing mystery of the Cepheid mass discrepancy.

The summer intern:
1) will reduce the already available Spitzer data using our data reduction pipeline;
2) will remove the light of the central star (using our PSF subtraction routines) to uncover the faint emission from diffuse matter that may have been ejected from the star;
3) will measure with high precision the brightness of each star, and derive the (still poorly characterized) period-luminosity relation (the Leavitt Law) of the sample in the IRAC bands.
The results will be presented available to the community at the January 2010 AAS meeting and will be the base for a refereed publication.

INTERN: Li-Wei Hung (Ohio State University)

ADVISORS: Dr. Saeqa Vrtilek, Dr. Ryan Hickox, Dr. Bram Boronson

PROJECT TITLE: Suzaku X-Ray Spectra and Pulse Profile Variations during the Superorbital Cycle of LMC X-4

Abstract:
An X-ray binary is a system containing a normal star orbiting a compact object, where the compact object is either a neutron star of a black hole, and the normal star fills its Roche lobe. In particular, X-ray pulsars are rotating neutron stars that are powered by material accreted from the normal companion. Because X-ray publsars have strong magnetic fields, the matter follows the fields and falls into the magnetic poles, generating pulses as themagnetic poles rotate in and out of our line-of-sight. While the general picture of the accretion mechanism is well known, the physics of the accretion near the magnetosphere, where the neutron star's magnetic field begins to dominate the flow, is not fully understood. By studying individual X-ray pulsars in detail, we hope to gain a better understanding of the accretion mechanism.

In this project the student will study the X-ray binary LMC X-4, consisting of a 1.25 solar mass neutron star accreting from a 14.5 solar mass O8III companion. In addition to the pulse period and orbital period, LMC X-4 has been observed to have a long-term period (the superorbital period) caused by a precessing accretion disk that periodically obscures the neutron star. The student will determine an improved value for the superorbital period of LMC X-4 based on 13 years of RXTE and ASM data, and use it to accurately determine the superorbital phase of three new Suzaku observations. The student will analyze the phase-averaged X-ray spectra and energy-resolved pulse profiles for the Suzaku observations, and interpret them in terms of as simple model based on the reprocessing of hard X-rays by the precessing accretion disk. This should result in a journal-worthy paper.

INTERN: Nathan Sanders (Michigan State University)

ADVISORS: Dr. Nelson Caldwell, Dr. Jonathan McDowell

PROJECT TITLE: HII Regions and Planetary Nebulae in M31

Abstract:
M31 is the nearest galaxy similar to our own, and the advent of large ground based telescopes and the Hubble telescope has recently made it possible to study individual parts of that galaxy with nearly the same level of detail as has been done in the Milky Way. Specifically, star clusters, HII regions, planetary nebulae and individual bright stars have been cataloged, and observed via direct imaging and optical spectroscopy. These data sets can be used in studies of ages, abundances and velocities of various components.

With the MMT, I have collected spectra of over 3000 objects of those various objects in M31. The spectra of HII regions and planetary nebulae in particular can be used to measure gas-phase abundances, and thus determine the radial abundance distribution in that galaxy, something that was last done over 25 years ago, and even then using very little data. The abundance distribution can then be used to determine the galaxy's formation history and map out evidence of mergers. The work will involve measuring the emission lines of the spectra, developing programs to use line ratios to determine electron densities, electron temperatures and then the Oxygen to Hydrogen abundance ratios.

INTERN: Evan Schneider (Bryn Mawr)

ADVISORS: Dr. Andrea Dupree, Dr. Nancy Brickhouse

PROJECT TITLE: Optical and Xray Signatures of Accretion in TW Hya

Abstract:
A fundamental characteristic of low mass star formation is the accretion of material from a circumstellar disk, channeled by magnetic fields, to the stellar surface. One nearby star, TW Hya is the closest accreting T Tauri type star. This object presents a unique opportunity to relate accretion signatures in the optical spectrum to the high energy emissions in the X-ray regime to understand the physics of the accretion process and its relation to a magnetically-active stellar corona.

We carried out a world-wide ground based campaign simutaneously with a long CHANDRA observation of the X-ray spectrum of TW Hya. High resolution optical spectra were obtained of TW Hya with MIKE on the Magellan telescopes that can be used to evaluate the presence of 'optical veiling' thought to be produced by the accretion continuum.

We want to know whether the amount of veiling and its variation are related (or not) to the X-ray line emission. This will help to identify the contributions of both accretion and coronal activity to the X-ray emission, and determine the characteristics (steady or impulsive) of the accretion process.

The data (both X-ray and optical) are in hand and are reduced and ready for analysis. Software required includes IDL, and IRAF and possibly specialized routines developed for this analysis. IDL will be used in analysis mode as well as for developing plotting routines. Simple statistics of means and variations will be used.

INTERN: Allison Strom (University of Arizona)

ADVISOR: Dr. Aneta Siemiginowska

PROJECT TITLE: Emission processes in parsec scale jets: sub-millimeter and X-ray connection

Abstract:
We will study non-thermal emission processes in quasars monitored by SMA (sub-millimeter array). The observed non-thermal spectral energy distribution from radio-gamma-rays is typically associated with the parsec scale jet emission. In such model the observed radio spectrum is due to the synchrotron emission from relativistic particles. The main emission processes contributing to X-rays and gamma-rays are related to the Inverse Compton scattering of the soft'' photons by the relativistic particles. In the Synchrotron Self-Compton (SSC) process the synchrotron photons emitted by the relativistic particles are Compton scattered by the same population of particles. In the External Radiation Compton (ERC) process the seed photons are located outside a jet/shock region.

The sub-millimeter and millimeter wavelengths probed by the SMA are critical to understanding the spectrum of relativistic particles that are being accelerated within the core of the blazar source. The particles that are responsible for the observed synchrotron emission at ~300~GHz have Lorentz factors ~10^4 (for the expected magnetic field of ~mGauss). These particles are responsible for upscattering the IR and optical photons to GeV energies and are directly responsible for the observed gamma-ray emission. Thus the variability observed in the millimeter wavelengths gives the immediate information about a change in the population of relativistic particles in the emitting region. Any increase in the total flux in the millimeter band must be related to a fresh population of newly accelerated particles. The variability in the spectral shape gives us additional measure of the particle energy distribution that is important for inverse Compton modeling of the high energy emission observed in X-rays and gamma-rays.

A sample of quasars that are bright in the sub-millimeter band has been monitored with SMA and there is a set of lightcurves available in the archive. We will characterize these lightcurves for each source and study the sub-mm properties of these quasars. Do they all vary? Is there any characteristic timescale? Are there any similarities between different type of sources in their variability? We will also collect the available archival X-ray and gamma-ray data to construct the spectral energy distribution for the observed sources. This will allow us to study correlations between different wave bands and also discriminate between different classes of sources. We will estimate basic physical parameters that are required to generate the observed SED for the sources in the SMA sample.

INTERN: Anthony Wong (Ohio Wesleyan University)

ADVISOR: Dr. Soeren Meibom

PROJECT TITLE: A study of rich clusters of stars in our Galaxy through high-resolution multi-object spectroscopy

Abstract:
Clusters of stars born together in the same time and space, are critical to our understanding of how stars form and evolve, and lay the foundation for a wide range of studies in astrophysics. The intern working with me will learn about stars and star clusters, and how to use high-resolution spectra of stars to determine their properties, whether they are members of a cluster or not, and if they have any close unseen companions. There will be several possibilities for astrophysical study upon completion of the data analysis - incl. stellar evolution, the evolution of stellar rotation, comparative studies of single and binary stars, and stellar and cluster dynamics. The intern will not have to write new computer code, but will work with existing codes running on the Center for Astrophysics super-computer cluster. The intern will not have to acquire new data for his/her project, but if observing is scheduled during the summer period, the intern will be included in the preparations for the observations, and possibly in the observing.

## 2008 Interns

List of colloquium talks given during the summer of 2008
Program of the SAO Summer Intern Symposium, August 13, 2008
2008 Summer Program Calendars for June July , and August
Abstracts for posters presented at the January, 2009 AAS meeting

INTERN: India Anderson (Southern University)

ADVISOR: Dr. Leonard Strachan

PROJECT TITLE: Testing Solar Wind Models with data from the SOHO Ultraviolet Coronagraph Spectrometer

Abstract:
One of the major discoveries from the SOHO Ultraviolet Coronagraph Spectrometer is that ions in the solar corona are heated to much higher temperatures than the electrons. This result has had a major impact on what solar physicists think about coronal heating and solar wind acceleration. Now with more than a solar cycle's worth of UVCS data we are in a position to test theoretical solar wind models over a wide range of coronal conditions. This project will test the latest MHD solar wind models for their accuracy and self-consistency in predicting plasma parameters in the corona.

INTERN: Dan D'Orazio (Juniata College)

ADVISORS: Dr. Greg Dobler and Dr. Beth Willman

PROJECT TITLE: Finding Invisible Galaxies with Gravitational Lensing

Abstract:
If an asteroid were traveling through space in a straight line and happened to pass near a massive object like the Earth, it would feel the gravitational pull of the Earth and its trajectory would be bent. A similar phenomenon occurs for light rays (photons), and the bending of a photon path by the gravitational pull of a massive body is called Gravitational Lensing. Gravitational lensing offered the first proof of Einstein's theory of general relativity in 1919 when, during a solar eclipse, the light from stars behind the sun was found to be bent by the gravitational pull of the sun. Gravitational lensing is observed when the light from a very distant object, such as a galaxy or a quasar is bent by the gravity of an (also very distant) object such as a galaxy or cluster of galaxies. For cases of near perfect alignment, i.e. when the background quasar is almost directly behind the foreground galaxy, gravitational lensing can cause the quasar to be split into multiple images. This type of lensing, where the background object is severely distorted by the lens galaxy is called strong lensing. Not only does strong lensing provide striking and spectacular astronomical images, the properties of the images, namely their positions and brightnesses, contain detailed information about the gravitational potential of the lens galaxy. With the gravitational potential, we can infer the distribution of matter in lens galaxies which are otherwise too far away to study with other techniques. In fact, lensing has already been proposed as a tool for studying the missing satellites problem. The Milky Way galaxy is surrounded by many smaller satellite galaxies. However, the problem is that detailed computer simulations of the Milky Way indicate that there should be more than ten times as many satellite galaxies than are actually observed. A possible solution is that the satellites are there but that they do not contain stars or gas and are invisible or dark. At present, gravitational lensing is the only way to detect the presence of dark matter in distant galaxies, and it has been suggested that the brightnesses and positions of images in multiply imaged quasars provide evidence for the existence of the missing satellites in distant galaxies.

My research on the gravitational lensing approach to this missing satellites problem has relied heavily on the available data. Basically I have built models which describe the gravitational potential of the lens galaxy plus satellite galaxies and used the data to constrain the parameters of the model (e.g. how massive are the satellites, where are they located relative to the lensing galaxy, etc.) Presently there are very few multiply imaged quasars that can be used for this purpose, but with upcoming surveys (such as PanSTARRS, in which Harvard-CfA is a partner) this will change dramatically. In the anticipation of the influx of new data, I would like to extend the simple modeling that has been done in the past to include more realistic satellite populations - as determined by the most recent simulations of the Milky Way - and apply these models to the presently available data. The work is theoretical/computational in nature and encompasses a broad range of astrophysics, from the dark matter halos of distant galaxies, to the satellite population derived from simulations, to the physical size of the background "source" quasar.

INTERN: Christene Lynch (Gettysburg College)

ADVISORS: Dr. Gerardo Juan Manuel Luna and Dr. Scott Kenyon

PROJECT TITLE: Time resolved optical spectroscopy of RS Oph after 2006 outburst

Abstract:
Symbiotic stars are binary systems in which a white dwarf accretes from a red giant wind which forms a dense nebula surrounding the system. Observationally, their optical spectra consist of various absorption bands from the red giant's photosphere, a blue continuum from the white dwarf photosphere and various emission lines from the ionized nebula. Some symbiotic system (e.g. RS Oph, T CrB) have massive white dwarf (M~1.35 Msun) as accretors. These systems, known as recurrent novae (Sokoloski et al. 2006, Nature, 442, 276), experience quasi-periodic outburst triggered by the accumulation of material onto the white dwarf surface.

The recurrent nova RS Oph went into outburst in 2-12-2006. During this event ~10^{-7} Msun were ejected from the white dwarf surface with velocities ~5000 km/s. Since then, this material is expanding and its density and temperature dropping. A few days after the 2006 outburst, extensive observational campaigns were performed in various wavelengths ranges, from X-rays to radio. We obtained approximately 200 low-spectral resolution optical observations during ~4 months after the outburst using the TILLINGHAST telescope together with the FAST spectrograph.

Optical spectroscopy of nova shell is used to investigate the chemical composition of the nebula, its ionization state, source of radiation and expansion rate (see e.g. Augusto & Diaz, 2003, AJ, 125,3349). With the available data, the student will be able to measure the evolution of these parameters as the shell is expanding, mapping its different stages and provide answers to questions as: is the accretion disk reconstructed? when?, are the nebular abundances compatible with a normal red giant wind or there was some chemical enrichment during the thermonuclear outburst?, what is the temperature evolution of the accreting white dwarf?

INTERN: Greg Mosby (Yale University)

ADVISORS: Dr. Lori Allen and Dr. Kevin Covey

PROJECT TITLE: Properties and Evolution of young stellar clusters in Orion

Abstract:
We recently used the Spitzer Space Telescope, NASA's premier infrared platform, to completely survey the giant molecular clouds in Orion, the nearest massive star-forming region to the Sun. Our Spitzer data reveal thousands of newly discovered young stars in these clouds. To better characterize these objects, we are using the state-of-the art, multi-fiber (Hectospec) on the 6.5-meter MMT telescope of Mt. Hopkins Arizona to acquire classification spectra. So far we have collected spectra for several hundred stars. These spectra, along with the mid-infrared data from Spitzer and near-infrared photometry from the Two Micron All Sky Survey (2MASS), wil allow us to examine fundamental questions related to the timescales for evolution and dissipation of protoplanetary disks, the characteristic lifetimes of molecular clouds, the predominance of triggered star formation, and the dynamical evolution of clusters.

The interested student will first perform the task of merging the spectroscopic and photometric data into a single database, then will use this information to construct Hertzsprung-Russell diagrams, and, by comparing to pre-main sequence evolutionary models, estimate the ages, masses, and disk properties of the young stars. In the course of this work, the student will learn about star formation, the evolution of protoplanetary disks and the timescales for planet formation. S/he will also gain experience using standard astronomical software such as IRAF, and more general software like IDL.

INTERN: Katherine (Kaylea) Nelson (Colby College)

ADVISOR: Dr. Ewan O'Sullivan

PROJECT TITLE: A combined Chandra/XMM-Newton study of nearby elliptical galaxies

Abstract:
The Chandra and XMM-Newton X-ray observatories have vastly increased our knowledge of nearby galaxies, providing both exceptionally sharp images and the sensitivity needed to probe for faint X-ray emission. However, most studies of ellipticals have focused on the brightest, best known systems, particularly those which reside at the centers of galaxy clusters, whose properties are primarily a product of their surrounding environment rather than their formation history. We have embarked on a project to develop a more representative view of the X-ray properties of elliptical galaxies, using a statistically complete sample of ellipticals observed by Chandra and/or XMM.

The aim of the project is to characterize the X-ray properties of ellipticals in the local Universe, which host three main classes of X-ray source; diffuse gas with temperatures of a few million Kelvin, the active nucleus, and X-ray binaries. With this sample, we hope to be able to address issues such as:

1) What fraction of nearby ellipticals have stable, gravitationally bound gas halos? What is the temperature and metal abundance structure of these halos, and is it correlated with factors such as stellar population age and nuclear activity?

2) How large is the variation in the luminosity of the X-ray binary population, and how is it related to properties such as galaxy mass and globular cluster population?

To address these issues we will measure the relative contributions of the AGN, X-ray binaries and diffuse emission, determine the spectral properties and structure of the hot gas halo, and examine the X-ray binary luminosity function. Comparison with HST imaging data (where available) and with radio and optical data from the literature will provide further information on galaxy structure, the stellar population and AGN activity.

A student working on this project will learn how to analyze X-ray and optical data using existing, well-tested software (CIAO, SAS, HEASOFT, IRAF), and carry out comparisons between Chandra, XMM-Newton and HST data. We have ready-made scripts and tasks to carry out parts of this analysis, which will be used by the student. Since the overall sample is too large to be analyzed in the short period available, the student will focus on a subset of 6 galaxies with good quality Chandra and XMM data, covering the more poorly-know faint end of the optical luminosity range, and including examples of both gas-rich and binary-dominated systems. The sample size can be adjusted depending on the progress of the student and data from a further 10 systems whose XMM observations have already been analyzed can be included in the final comparisons. As well as experiencing the process of analysis and interpretation of scientific data, the student will learn about the relative diagnostic capabilities of different wavebands and instruments, the structure and properties of elliptical galaxies, the different classes of X-ray source they host, and the physical mechanisms behind their emission.

INTERN: Arpita Roy (Franklin & Marshall College)

ADVISOR: Dr. Elizabeth Humphreys

PROJECT TITLE: What does High-Mass Star Formation "Look" like? Accretion and Outflow Close to a Forming High-Mass Star

Abstract:
High-mass star formation is difficult to study relative to the low mass case partly because high-mass stars evolve more rapidly and are rare. Because there are not many examples of high-mass star formation close by, it is important to study the few that there are in detail so that we can determine the key processes involved.

I have two projects relating to the formation of the closest forming high-mass star, Source I in Orion. With collaborators in the Radio and Geoastronomy Division at CfA, we have been working to characterize the nature of the accretion and outflow process of Source I using very high resolution (milliarcsecond) radio interferometry observations of molecular maser emission. The first project within our group is performing modeling to work out the geometry of the forming star (e.g., disk plus outflow) and its 3D orientation. We have programs developed for this use already. The second project is to perform radiative transfer modeling of emission from the source to work out the temperature and density of the gas. Again we already have programs that perform the calculations. The results will be reported in a publication and/or at the AAS.

INTERN: Greg Salvesen (University of Michigan)

ADVISORS: Dr. John Raymond and Dr. Dick Edgar

PROJECT TITLE: Cosmic Ray Pressure in the Cygnus Loop

Abstract:
Models of cosmic ray acceleration in shock waves predict either very efficient or very inefficient acceleration, with a ratio of cosmic ray to gas pressure (P_cr=P_g) near 80% or below 10%. Intermediate values are unstable. P_cr is hard to measure, but it can be inferred because the ram pressure, rho*V^2, nearly equals P_cr + P_g. Halpha filaments of a non-radiative shock delineate the northern 1/3 of the outer edge of the Cygnus Loop supernova remnant. Their proper motion is about 5 arcseconds between the first and second epoch Palomar surveys. An upper limit to the distance to the Cygnus Loop is given by the distance D to a star whose spectrum shows high velocity, high temperature absorption lines from the shocked gas. The combination of distance and proper motion gives V. The temperature can be determined from the X-ray spectrum, and high quality ROSAT PSPC spectra exist for the entire region (Levenson et al. ApJ 526, 874). From the upper limit to V and the lower limit to Tx one can derive an upper limit on P_cr=P_g. We propose that an REU student measure the proper motions for about 50 segments along the northern Cygnus Loop and fit the ROSAT spectra for the corresponding post-shock regions. We have tried this for one segment where we and our collaborators have obtained optical line profiles and UV spectra (Ghavamian et al. ApJ 547, 995; Raymond et al. ApJ 584, 770), and P_cr=P_g < 0.60 for the upper limits on proper motion and D and lower limit on Tx, and P_cr=P_g < 0.06 for the nominal values of proper motion, D and Tx. Measuring 50 independent regions will reduce the uncertainty and probably provide a limit somewhere between these values. To our knowledge, this sort of analysis has never been published for any SNR shock.

INTERN: David Stark (University of Minnesota)

ADVISORS: Dr. Paul Nulsen and Dr. Ralph Kraft

PROJECT TITLE: Jets in Cen A

Abstract:
When matter falls into the black hole at the center of a radio galaxy, some of the energy released is funneled into powerful opposed jets. These flow out and interact with gas surrounding the galaxy, driving it out of the way, creating shocks and inflating lobes of radio emitting plasma. Such effects can be seen in radio and X-ray images of many radio galaxies. A particularly good example is provided by the nearest radio galaxy, Centaurus A (Cen A).

We do not yet know what radio jets are composed of. They emit synchrotron radiation, showing that they contain relativistic electrons and magnetic fields, but there is good reason to believe that these only represent a small component of jets. Positively charged particles are needed to keep jets neutral (otherwise electrostatic forces would prevent them escaping the nucleus). These could be ions (mostly protons) or positrons. The ions may be relativistic or non-relativistic and there may also be other non-relativistic matter swept up in jets.

One step to determining the composition of a jet is to know its equation of state. In contrast to more distant radio galaxies, Cen A is close enough that its eastern radio jet is well resolved in X-ray observations with Chandra. This enables us to measure the size of the jet and its pressure distribution. The aim of this project will be to use the equations for relativistic fluid flow to relate these properties and determine the equation of state of the jet plasma. That information will be used to constrain the composition of the jet.

INTERN: Caleb Wheeler (University of Missouri Columbia)

ADVISOR: Dr. Guillermo Torres

PROJECT TITLE:   Binarity in the Pleiades Cluster

Abstract:
The open star cluster known as the "Seven Sisters" (Pleiades) is one of the most prominent in the northern sky. It has been studied by astronomers for at least a century. We are currently engaged in a long-term radial-velocity survey of more than 200 of its members, and one of the goals of this project is to study the binary population in the cluster. In particular, we are interested in investigating the effects of tidal forces in binaries, which tend to synchronize the rotation of the components to the mean orbital motion, and tend make the orbits circular with time. These processes are not yet fully understood theoretically.

We are seeking a motivated student who is interested in learning about stars and the techniques used to study them. The work will involve the determination of spectroscopic parameters of cluster members (mainly the effective temperatures and projected rotational velocities) on the basis of more than 3000 optical spectra accumulated over more than 20 years with the same instrument. For the binary stars, the student will derive radial velocities using existing software, and will incorporate also historical radial velocities available from the literature, to supplement our own measurements. Spectroscopic orbits based on these velocities will be derived both for single-lined binaries and double-lined binaries. We hope to significantly increase the number of spectroscopic binary systems in the Pleiades. This information will be used to construct the eccentricity versus Log period diagram, one of the most useful diagnostics of the efficiency of orbital circularization. This will be used to infer the circularization timescale for the Pleiades, which can be compared with theoretical predictions.

The spectroscopic parameters for single stars will be used to study the rotational properties of members as a function of spectral type. Their radial velocities, along with the center-of-mass velocities of the binaries, will be used to determine the internal velocity dispersion in the Pleiades. If time permits, we will also use the radial-velocity information to study the kinematics of the cluster.

INTERN: Angie Wolfgang (Cornell College)

ADVISORS: Dr. Paul Green and Dr. Kevin Covey

PROJECT TITLE: Characterizing X-ray Active Objects in the ChaMP Survey

Abstract:
The Chandra Multiwavelength project (ChaMP) is a wide-area X-ray sky survey encompassing nearly 19,000 newly-discovered X-ray sources. New spectroscopy has been obtained for hundreds of optically bright objects. These spectra will help us to measure for the first time the true fraction of nearby galaxies that harbor actively-fed supermassive black holes, and will also allow us to understand the strange excess blue emission from X-ray active stars in our own galaxy. We seek a student to assist in the analysis of spectroscopy from the FAST spectrograph at the FLWO1.5m on Mt Hopkins of optically bright, X-ray active stars, galaxies and active galactic nuclei obtained as part of the ChaMP. This includes analysis and verification of spectra for radial velocities using IRAF, characterization of the object types by comparison to templates, compilation of results in a Sybase database for uniform tabulation and easy retrieval. Final products will be incorporated into the existing ChaMP database, which will become public after journal publication of results.

## 2007 Interns

INTERN: Eric Baxter (Harvey Mudd College)

ADVISORS: Dr. Gus Covey, Dr. August Muench
PROJECT TITLE: The Distance to NGC 2264

Abstract:
Unavailable.

INTERN: Iara Cury (Yale University)

ADVISORS: Dr. Rosanne di Stefano, Dr. Pavlos Protopapas
PROJECT TITLE: Stellar Variability in the MACHO Data Set

Abstract:
Stellar variability is the key to understanding many stellar systems. Pulsations provide information about the state of a star; orbital effects can be used to measure stellar masses; star spots and even clouds in the atmospheres of low-mass dwarfs also cause variability. During recent years, the microlensing teams have monitored tens of millions of stars. Their data sets contain records of the variability of many types. Some of these observations have been exploited already; for example Cepheids and eclipsing binaries have been well studied. The more subtle types of variability have yet to be explored. We have carried out a preliminary analysis of the MACHO data set and find evidence of possible new types of stellar variability. The project we propose would involve a systematic examination of this variability using the techniques of wavelet analysis. On the scientific side, the results could have implications fore the study of stellar systems, since several percent of all stars in our sample show unusual variability. On the technical side, the results will be to provide a new tool for the study of variability, one which can be applied to a wide range of data sets. This will prepare us for the huge influx of data from the new surveys like Pan-STARRS and LSST. This work will be done in collaboration with the Initiative of Innovative Computing at Harvard University.

INTERN: Furqan Fazal (Amherst College)

ADVISORS: Dr. Sridharan Tirupati, Dr. Quizhou Zhang
PROJECT TITLE: Massive stars are the dominant ingradients of galaxies

Abstract:
Massive stars are the dominant ingradients of galaxies. Throughout their lives they inject enormous amounts of energy and momentum into the interstellar medium from which all stars form. Starting with powerful outflows and ending in supernovae which result in exotic object like neutron stars and pulsars their influence is far-reaching. However, the births of the massive stars are shrouded mystery. In studying their origins, we are primarily hampered by their small numbers, large distances, fast evolution and obscuration by dust. The SPITZER telescope, using its infrared detector, is able to peer through the dust and has produced a valuable resource called GLIMPSE, which is a systematic imaging survey of large portions of our Galaxy. In the proposed project, a summer student can use this image database to study the environments of a sample of high-mass proto-stellar objects (HMPOs) which contain massive stars in the earliest stages of their lives. We have studied this sample at other wavelengths and the summer student will get the first glimpse of their characteristics as imaged by SPITZER. Using images at multiple wavelengths, we will classify objects in the immediate vicinity of the luminous HMPOs, identify the most massive and youngest memebers and study their spatial distribution to understand the nature of star clusters in their earliest stages.

INTERN: Sarah Harrison (Massachusetts Institute of Technology)

ADVISORS: Dr. Dan Evans, Dr. Julia Lee
PROJECT TITLE:   Energetic processes in the environments of Active Galactic Nuclei

Abstract:
Active galactic nuclei (AGN) are among the most energetic astrophysical phenomena in the Universe. Powered by accretion onto a supermassive black hole, they are often observed to eject twin jets of particles at relativistic speeds out to very large distances from their centers. The Chandra X-ray Observatory has revolutionized our understanding of the energetic processes involved in AGN, through detailed studies of how jets interact with their hot-gas environments. In several cases, the energies of the X-ray gas environments exceed 1060 ergs, and giant cavities in the X-ray gas are often seen, believed to be the result of an jet expanding into its ambient medium.

This 10-week project will allow the REU student to (1) learn how to reduce Chandra data, (2) perform imaging and spectroscopy of the nucleus and thermal gas of several nearby AGN, and (3) combine these data with observations at radio and optical wavelengths to better understand the physical conditions present in active galaxies.

Clusters of galaxies are the most massive gravitationally bound objects in the universe. They formed relatively recently in the history of the universe, so we can try to measure their evolution directly. This project will focus on understanding the evolution of cluster and galaxy properties in a sample of clusters at moderate redshift. These clusters have been observed with Chandra, Spitzer, and ground-based optical telescopes. We will analyze infrared images of the clusters to identify likely cluster members and estimate the stellar masses of the galaxies and the clusters. If time allows, we will compare these properties to the X-ray and mid-infrared properties of the clusters. These detailed comparisons will be critical for using future cluster surveys to probe dark energy.

The abundance of clusters and groups in the nearby universe is a powerful constraint on cosmological parameters. In particular, the anisotropies seen in the microwave background should grow to form the clusters we see today. We have used the Sloan survey to measure the abundance of clusters in the nearby universe, but measuring the abundance of groups is more difficult. We have begun a survey of groups outside the Sloan survey region to measure the abundance of these lower-mass systems. The project will involve compiling the existing and new data to measure group masses and use these to measure cosmological parameters. The project may involve an observing run to Mt Hopkins to operate a telescope and collect some of the data for the survey.

INTERN: Colin Hill (Massachusetts Institute of Technology)

ADVISORS: Dr. Ken Rines
PROJECT TITLE: Understanding Cluster Evolution / Nearby Clusters and Cosmology Nuclei

Abstract:
Clusters of galaxies are the most massive gravitationally bound objects in the universe. They formed relatively recently in the history of the universe, so we can try to measure their evolution directly. This project will focus on understanding the evolution of cluster and galaxy properties in a sample of clusters at moderate redshift. These clusters have been observed with Chandra, Spitzer, and ground-based optical telescopes. We will analyze infrared images of the clusters to identify likely cluster members and estimate the stellar masses of the galaxies and the clusters. If time allows, we will compare these properties to the X-ray and mid-infrared properties of the clusters. These detailed comparisons will be critical for using future cluster surveys to probe dark energy.

The abundance of clusters and groups in the nearby universe is a powerful constraint on cosmological parameters. In particular, the anisotropies seen in the microwave background should grow to form the clusters we see today. We have used the Sloan survey to measure the abundance of clusters in the nearby universe, but measuring the abundance of groups is more difficult. We have begun a survey of groups outside the Sloan survey region to measure the abundance of these lower-mass systems. The project will involve compiling the existing and new data to measure group masses and use these to measure cosmological parameters. The project may involve an observing run to Mt Hopkins to operate a telescope and collect some of the data for the survey.

INTERN: Therese Jones (Penn State University)

ADVISORS: Dr. Kelly Korreck
PROJECT TITLE: Particle Acceleration from the Solar Corona to the Earth

Abstract:
We are examining the way particles are accelerated and heated as they propagate from the solar corona to the earth. The student would be exposed to data from XRT on Hinode, ACE, ULYSSES, and SOHO satellites. Specifically they would be responsible for fitting distribution of protons from the ACE, Ulysses and SOHO satellite. Then they would use the XRT data to compare the initial conditions of these energetic particles. By fitting the proton particle distributions and looking at timing, we can get a sense of the changes the plasma undergoes as it moves through theheliosphere and where it deposits the energy. The student would be responsible for fitting the data sets and then helping prepare the paper. The student will get an introduction to solar physics, some statistical mechanics, data analysis, plasma astrophysics, image processing, and stellar winds. The student would also have an opportunity to present the work either at an SSP seminar or at a monthly meeting of the New England Space Science Consortium.

INTERN: Kyle Penner (University of Texas at Austin)

ADVISORS: Dr. Silas Laycock, Dr. Maureen van den Berg
PROJECT TITLE: Optical and infrared identifications of ChaMPlane sources

Abstract:
The Chandra Multiwavelength Plane (ChaMPlane) survey is a large project to study the properties of the various classes of low-luminosity X-ray point sources in our Galaxy. These include binaries with compact objects like white dwarfs or neutron stars that accrete gas from a companion star, but also stars like the Sun, and close binaries where the tidal forces between the stars make them spin fast. The instruments on the Chandra X-ray Observatory have unique capabilities to expand our knowledge of these X-ray sources. The sensitivity of Chandra allows us to detect systems out to large distances; and thanks to Chandra's unprecedented spatial resolution the positions of these X-ray sources can be measured with a precision like never before, which is extremely important for follow-up studies and source classification. ChaMPlane makes use of archived Chandra images that were taken when Chandra was looking at objects that lie in directions close to the Galactic plane. Typically, the astronomers that have made these images are only interested in one object, but many more are detected. We process these images and try to classify all the sources, first by taking optical and near-infrared images to identify the objects that emit the X-rays, and finally by taking spectra to determine the source class. Currently, the ChaMPlane X-ray database includes almost 14000 point sources detected in about 120 discrete fields, that are covered by more than 200 Chandra observations. Deep optical images in three broad- and one narrow-band filter (V, R, I and Halpha) have been taken for all of them, and although far from complete, our spectral database is steadily growing with classification spectra being taken for more than 2700 candidate counterparts.

The REU summer internship will allow students to become familiar with several aspects of the ChaMPlane project. We suggest two possible projects from which the student can choose:

1) The goal of the first project is to characterize the properties of the brightest of the ChaMPlane sources. The first phase involves fitting X-ray spectra, from which we derive constraints on

a) the process that creates the X-ray emission (accretion versus magnetic activity), and

b) the amount of extinction (and consequently the distance) between us and the source. Currently there are between 50 and 75 such bright ChaMPlane sources (excluding sources close to the Galactic Center). In the second phase, a search for the optical counterparts will be done using the available optical/infrared data while taking into account the X-ray constraints on the source classes and distances.

2) Some parts of the Galaxy are heavily obscured by clouds of dust and gas that prevent us from seeing what is behind them when we use optical images. The effects of extinction are less severe in the near-infrared. The ChaMPlane near-infrared images serve to look for counterparts of obscured X-ray sources, but a lot more can be learned from them. For example, candidate star clusters, previously identified by other groups in lower-resolution images, can be studied with a "sharper view" and a search for more candidate clusters can be done. Potentially associated X-ray sources can then be used to learn more about both the clusters and X-ray sources, like their distances and when/how they were formed. Close examination of the infrared images can lead to other interesting discoveries (and possible X-ray counterparts), like planetary nebulae that are formed when a low-mass star expels its outer layers at the end of its life (in an initial examination we have already found one new planetary nebula).

The colors of a star are sensitive to the amount of gas and dust through which we see it. Another application of this infrared project is to derive a relation between the infrared and X-ray colors of ChaMPlane sources, which can then be used to constrain an X-ray source's distance even when no obvious counterpart is found; information on distances is crucial to study the distribution of X-ray sources in the Galaxy.

Both projects are suitable for a poster presentation at the January 2008 AAS meeting. Throughout the 10-week period, the student will have the opportunity to interact with different ChaMPlane group members, and experience what it is like to be part of a research group. For more details on ChaMPlane, visit http://hea-www.harvard.edu/ChaMPlane.

INTERN: Megan Reiter (University of California Berkeley)

ADVISOR: Dr. Massimo Marengo
PROJECT TITLE: An IRAC view of Galactic Asymptotic Giant Branch Stars

Abstract:
The Sun, towards the end of its life, will become an Asymptotic Giant Branch (AGB) Star. Once exhausted its primary Hydrogen nuclear fuel, it will ultimately become 10,000 more luminous than today, and swell beyond the orbit of our planet, that will be engulfed and vaporized. This act of destruction, however, will also be an act of creation: it is in the nuclear furnaces of AGB stars that most of the carbon, the basic element of life, available in the Galaxy is synthesized. This carbon, together with other heavy elements, is slowly released to the circumstellar environment in the form of a dusty wind, that gradually surrounds the star with a thick opaque cocoon. Like a butterfly from the chrysalis, the cocoon will ultimately burst to give rise to a Planetary Nebula, one of the most beautiful and ephemeral objects in the sky, leaving behind a white dwarf. The carbon and the other elements released in the AGB wind will merge with the interstellar medium, ready for a new cycle of stellar and planetary formation: the carbon atoms in our body have likely been produced in an AGB stars billion of years ago.

INTERN: Blake Sherwin (Cambridge University)

ADVISOR: Dr. Avi Loeb
PROJECT TITLE: Hypervelocity Stars from the Andromeda Galaxy

Abstract:
Unavailable.

INTERN: Johanna Teske (American University)

ADVISOR: Dr. Andreas Zezas
PROJECT TITLE: A combined Chandra/Spitzer study of galaxy mergers

Abstract:
We have embarked on a multiwavelength program to study the relation between galaxy interactions and the level and type of activity they induce. The main element of this program is Spitzer multiband imaging and spectroscopic observations of a large sample of nearby interacting galaxies. These data provide a view of the evolution of star-formation and AGN activity as a function of the stage and the parameters of the interaction. An independent picture of the activity in a subset of these galaxies, is given by X-ray observations, which provide diagnostics for the presence of AGNs and they allow us to study the evolution of X-ray binaries and hot gas in the different stages of galaxy interactions.In total 18 systems from the Spitzer sample have been observed with Chandra. These systems span the full range of interaction stages from weak interactions to coalescing galaxies. In particular the Chandra data will allow us to investigate: (a) how the discrete source and diffuse X-ray emission components evolve in the different stages of the interaction; (b) address the connection of Ultra-luminous X-ray sources with enhanced star-formation; (c) study the X-ray emission from the nuclei and search for the presence of AGNs. We will measure as a function of the merger stage: the relative contribution of the diffuse emission and the discrete sources in the overall X-ray emission of the systems; their relation with IR, optical and radio emission; the spectral parameters of the diffuse emission and the luminosity distribution of the discrete sources. Comparison with the already analyzed Spitzer data will identify emission components related with on-going star-formation. A student who will work on this project will learn how to analyze X-ray data using existing and previously tested software (CIAO, Sherpa), and perform comparisons between the X-ray, infrared and optical data. There are ready made scripts and tasks to do parts of this analysis which will be used by the student (after of course the required training). They will also analyze Spitzer data (as needed) again using existing and previously tested software. Since the overall sample is too large to be analyzed in such a short period of time, the student will focus on a subset of 10 objects with good quality Chandra data, spanning the full range of interaction parameters (the actual size of the sample can be adjusted depending on the progress of the student). The main focus will be on the analysis of the Chandra data and the comparison with data in other wavebands. This way the student will be exposed to the interpretation of scientific data and learn about galaxy interactions, star-formation and sources of X-ray emission in galaxies. They will be introduced to the physical mechanisms of emission in different wavebands and the different diagnostics we use in order to distinguish between them. Finally they will learn how to do background literature research on a specific topic.

## 2006 Interns

INTERN: Michael Anderson, University of Michigan

PROJECT TITLE: X-ray Bright Optically Normal Galaxies (XBONGs) in the XBootes Field
ADVISOR: Dr. Steve Murray
MENTORS: Almus Kenter, Ryan Hickox, Christine Jones, Bill Forman

ABSTRACT:
While X-ray surveys have shown that the X-ray background is due almost entirely to emission from broad line AGN, X-ray observations have also identified a class of galaxies which are X-ray bright (with typical luminosities of 1042 ergs/sec and thus generally assumed to be associated with accretion onto a supermassive black home), but whose optical spectra do not show emission lines, as would be expected from an AGN. The nature of these galaxies is presently unknown. One suggestion is that these XBONGS (X-ray Bright Optically Normal Galaxies) may be obscured, so that emission from their nuclei is not seen optically. Another possibility is that the galaxies are so bright, that the galaxy emission dominates the optical spectra. XBONGS also have been suggested to be BL Lac-like systems. A fourth suggestion is that these galaxies do not contain optically thick accretion disks, but instead have an advection donimated (ADAF) or radiatively inefficient accretion flow (RIAF). So far the number of XBONGS that have been identified and studied is relatively small (∼30).
In the XBootes Chandra survey, we have ∼200 XBONG candidates, X-ray luminous galaxies with absorption line optical spectra. With the large Bootes spectroscopic galaxy survey, one can determine the environment for each XBONG and compare their local galaxy density to that of broad line AGN, as well as to normal galaxies with similar optical magnitudes and colors. With this large sample, one also can measure the spatial correlation length and may also be able to measure the luminosity function for XBONGS. A comparison of their environment and X-ray properties (including spectra) to type 1 AGN and to normal galaxies may determine the nature of these unusual galaxies.

INTERN: Sarah Ballard (University of California Berkeley)

PROJECT TITLE:   Star Formation in Bright-Rimmed Clouds
ADVISOR: Dr. Lori Allen

ABSTRACT:
Bright-Rimmed Clouds (BRC) are relatively isolated molecular clouds near hot young O stars. They are recognized in the optical as small dark clouds, often having a cometary morphology, with an ionization front (bright rim) facing the direction of the ionizing stars. Because of their isolated, compact structure, their proximity to young high mass stars, and the presence of an ionization front, bright-rimmed clouds are excellent laboratories for studying triggered star formation. One such sample of BRC are currently being studied in a Spitzer GTO program. The sources were selected from the catalogs of Sugitani & Ogura (Sugitani, Fukui, & Ogura, 1991; Sugitani & Ogura 1994), who scoured optical sky survey plates and compiled a list of small clouds bounded on at least one side by a bright rim, and containing one or more IRAS sources having colors consistent with young stars. To date, no complete census has been obtained of the young stars in BRC, and their status as sites of triggered or sequential star formation remains unproved. With the Spitzer Space Telescope, we now have the ability to detect all of the young stars in these clouds, and to determine whether they contain protostars (evidence of very recent star formation triggered by their neighboring OB associations), or only more evolved T-Tauri stars (coeval with the OB associations). The researcher who takes this project on will perform photometry on the Spitzer data using a local photometry program written in IDL (author of the software, Dr. Rob Gutermuth, is here and will be available for consultation). After a brief period of verifying the photometry results (and tuning the program as needed), the researcher will compile photometry on the entire sample and do statistical studies of the young stellar content of these clouds. These include the multiplicity of sources, evolutionary state of the young stars, the frequency of protoplanetary disks, the spatial distributions, etc. It is anticipated that this work will form the basis for a paper suitable for publication in the Astrophysical or Astronomical Journal.

INTERN: Amy Colon (Hunter College)

PROJECT TITLE: Fabrication of Future X-ray Telescopes by Selective Deposition
ADVISOR: Dr. Suzanne Romaine
MENTOR: Ricardo Bruni

ABSTRACT:
Mirror figuring using selective coating deposition
We are currently involved in building a prototype optic for the Constellation-X Mission, the followup Mission to Chandra. Looking to the future of high spatial resolution X-ray optics, improving, or even meeting, the resolution of the Chandra telescope, especially under tight budget constraints of future missions, presents us with serious technical challenges and will strain our imagination and creativity.
Along these lines, we have a program to investigate the figuring of x-ray optics using fine control of the deposition of thin films to correct the figure of the optic. The proposed project will involve the student in a study of grazing incidence X-ray optics and will carry out a program of test coatings to understand and define the limits to which we can take advantage of this technology.
The proposed project will involve the student in the fabrication of materials and coatings which is necessarily an interdisciplinary experience. Several areas including: physics, astronomy, optics, materials science and engineering are applicable in this project.

INTERN: Adrienne Hunacek (Massachusetts Institute of Technology)

PROJECT TITLE: High Resolution Ultraviolet Spectroscopy of the X-ray Binary Cyg X-1
ADVISOR: Dr. Saeqa Vrtilek
MENTOR: Joey Neilsen

ABSTRACT:
Doppler Tomography of X-ray Binaries
This project is to construct "images" of x-ray binaries using the method of modulation tomography. The student will use existing data from the ESO archives to study the geometry of accretion flow in systems that contain neutron stars of black holes. The process is similar to that used in medical tomography. The images reconstructed via Doppler tomography provide unique and detailed insights into the structure of the accretion flow around compact objects. This should result in a short but interesting paper.

INTERN: Lauren Hund (Furman University)

PROJECT TITLE: Detecting AGN Through Variability in IRAC's Calibration Field
ADVISOR: Dr. Joseph Hora
MENTOR: Matthew Ashby

ABSTRACT:
The Spitzer Space Telescope is the fourth and final great observatory and has created entirely new opportunities to study and better understand objects in the distant, early universe. This is due to a combination of Spitzer's unprecedented sensitivity in the mid-infrared (3-10 microns) and its privileged position in a novel earth-trailing orbit, where the celestial backgrounds are very low and even thermal emission from the earth is minimized.
We are seeking a motivated student to work with existing Spitzer imaging data of a unique field, the IRAC Calibration Field (IRAC-CF). This particularly infrared-dark region offers an extremely deep view of extragalactic space, even by Spitzer standards. It has been observed for 1-5 hours every 1-4 weeks with Spitzer's Infrared Array Camera (IRAC) since December of 2003. This accumulation of data is expected to continue steadily for the remainder of the Spitzer mission, meaning that the infrared sensitivity will eventually be the deepest in existence, exceeding even the ultra-deep GOODS fields with four times the area.
One special attribute of this dataset is its temporal coverage -- since the field is observed roughly once every month, it is possible to find and characterize distant active nuclei (AGN, or supermassive black holes) in the infrared as they dim and brighten from month to month, and indeed several already have been found. These objects are also being observed monthly from the ground via coordinated R-band imaging at the Palomar 60", so as to correlate the infrared and visible-wavelength behavior of these objects. Other supporting observations with the other Spitzer instruments, HST/ACS, and Akari are either approved or already completed.
This project is well-advanced, but needs some careful attention before it can be brought to completion. The student would be responsible for verifying the existing detections of variable nuclei and for refining the images to isolate even more variable objects. The student will be taught how to use MOPEX (the Spitzer data reduction software) to improve upon the existing mosaics, and how to perform precise source photometry with SExtractor. The student would then manipulate the galaxy catalogs he/she created to examine the trending behavior of these active nuclei.

INTERN: Christopher Klein (California Institute of Technology)

PROJECT TITLE: The Spitzer Interacting Galaxies Survey: IRAC Evaluations of Star Formation
ADVISOR: Dr. Matthew Ashby
MENTORS: Drs. Andreas Zezas, Howard Smith

ABSTRACT:
The Spitzer Space Telescope is the fourth and final great observatory and has created entirely new opportunities to study and better understand fundamental aspects of star formation in galaxies. This is due to a combination of Spitzer's unprecedented sensitivity in the mid-infrared (3-10 microns) and its privileged position in a novel earth-trailing orbit, where the celestial backgrounds are very low and even thermal emission from the earth is minimized. New Spitzer results are being published every day, and are having a significant impact in many different fields.
We are midway through an approved Spitzer program to study whether and how star formation and nuclear activity within galaxies are influenced by major mergers, i.e., mergers between galaxies of comparable mass. Star formation has long been thought to result from triggering processes of various kinds, including supernovae shock waves and galaxy collisions. The student will have the opportunity to measure the basic set of observable quantities (luminosities, star-formation rates, morphologies) from newly-acquired Spitzer observations of numerous galaxy-galaxy pairs in various stages of merging. Specifically, we are seeking a motivated student to accomplish the following:

1. Process the galaxy images to create optimal mosaics in all four mid-infrared IRAC bands, using existing software with which our team is very familiar.
2. Quantify the amount and spatial extent of star forming activity in the sample galaxies, and search for trends with respect to merger stage and galaxy type. It is hoped that these data will allow us to assess a newly-developed understanding of how galaxies evolve in the infrared.
3. Apply simple criteria to detect active nuclei in cores of the merging objects.

The work outlined is substantial, but it ought to be feasible within the 10-week term of the REU appointment. We have decided to form a three-person team to advise the student. Ashby will serve as team leader and be responsible for the outcome of the REU project; Zezas will serve as backup when Ashby is (briefly) on travel and will help set the analysis strategies; Smith will help relate the results to the nascent galaxy evolution theory. If the student makes rapid progress, he/she may have an opportunity to analyze complementary MIPS 24 micron imaging observations as well, which will aid in the interpretation of the IRAC mosaics.

INTERN: Robert Penna (University of Rochester)

PROJECT TITLE: A Two-Fluid Plasma Shock Wave Model for the Strong Shock in Centaurus A
ADVISOR: Dr. Paul Nulsen

ABSTRACT:
Centaurus A (Cen A) is the nearest radio galaxy to us. Its active nucleus (black hole) pumps out energy in twin radio jets that interact with the surrounding interstellar medium creating radio emitting lobes of relativistic plasma. Energy is being pumped into the southwestern radio lobe fast enough to create a region of high pressure, that expands explosively and drives a strong, Mach 8, shock into the surrounding interstellar gas. In X-ray observations with the Chandra Satellite, the lobe appears as a cavity, surrounded by a region of bright X-ray emission that comes from the heated and compressed, shocked gas.
This is an example of a "collisionless" shock. Shocks are regions of rapid dissipation, where the kinetic energy of supersonic gas gets converted rapidly into thermal energy. Normally, this happens over distances that are similar to the mean-free-path of gas particles. In the plasma around Cen A, the kinetic energy of the protons gets converted into thermal energy much more quickly. However, the electrons still rely on the collisions to get their share of the energy from the protons, and this takes much longer. As a result, the electrons heat up relatively slowly, over distances that are resolved in the X-ray observations.
In a strong shock, like the one in Cen A, the final temperature of the gas depends only on the density of the gas before the shock and its pressure after the shock. The gas inside the lobe is expected to have the same pressure, but the density of the gas outside the lobe varies, so we would expect the shocked gas to have different temperatures around the lobe. It is a puzzle that all the shocked gas seems to have the same temperature. One possible project is to make a model for the collisionless shock around Cen A, to see if we can explain this puzzle, along with other features of the shock.

INTERN: Julia Sandell (Columbia University)

PROJECT TITLE: Recognizing Loops in the Solar Corona: A Diagnostic Tool for Magnetic Field Extrapolation Models
ADVISOR: Dr. Vinay Kashyap
MENTORS: Drs. Ed DeLuca, Mark Weber

ABSTRACT:
The corona on the Sun is made up of very hot plasma (greater than a million degrees) that is threaded and maintained by a pervasive magnetic field. It is believed that the corona is heated to such high temperatures because of the energy released when highly stressed magnetic fields reconnect and relax to a lower potential configuration. The three dimensional structure of the magnetic fields is therefore of much interest. There exist methods that extrapolate the 3D fields from surface flux measurements, and the extrapolated field lines are then validated by comparing with high-resolution EUV images of the solar corona from TRACE. We are now developing a process by which this validation can be done automatically, by comparing the field lines to morphologically identifiable coronal loops. The intern will take an active part in the development of the morphological loop finding method using TRACE data, and in adapting the magnetic field extrapolator to work for future solar missions.

INTERN: Sarah Scoles (Agnes Scott College)

PROJECT TITLE: Optical Counterparts to Supersoft X-ray Sources in the Nucleus of M31
ADVISOR: Dr. Rosanne diStefano

ABSTRACT:
Soft X-ray sources have been studied for only about 15 years. Some may be progenitors of Type Ia supernovae. Some may be black holes. Others may be soft states of X-ray sources that can also exhibit hard states. We are conducting research along several fronts to study soft X-ray sources in other galaxies. Three projects are ideal for a summer intern. (The intern would choose the project.) One of these would be to conduct research to follow up on clues that soft X-ray sources are more common in the vicinity of supermassive black holes. Chandra data from the central regions of a set of nearby galaxies will be studied to determine if there is a genuine excess of soft sources and to quantify and understand the effect, if it is verified. It has been postulated some of these stripped soft sources could be the stripped cores of giant stars that have been tidally disrupted by the supermassive black hole. The second project would be to work with a rich archive of HST observations of the center of M31. This work will explore the connections between X-ray sources and optical emission in the vicinity of the black hole. Finally, we have a suite of ongoing theoretical projects designed to understand the fundamental natures of soft X-ray sources, particularly near galaxy centers.

INTERN: Michael Shaw (Massachusetts Institute of Technology)

PROJECT TITLE: Recovering Long-Term Lightcurves from the Harvard Plates: A Search for Eclipsing Binaries in M44
ADVISOR: Dr. Josh Grindlay
MENTORS: Bob Simcoe, Silas Laycock

ABSTRACT:
The world's fastest (by 2006) astronomical plate scanner has been just completed and commissioning runs will begin with this project to digitize a century of Harvard plates on the galactic cluster M44. This inauguration of the Digital Access to a Sky Century from Harvard (DASCH) project will digitize (at only 20sec each) at least ∼100 plates (typically 8 x 10in) containing historical (c. 1890 - 1990) images of the open cluster M44 (the Beehive Cluster). Using the well-calibrated stars in this cluster, this will further develop astronomical photometry analysis routines for the digitized plate images and allow a search for eclipsing binaries, and other variables, within or beyond the cluster. New binaries may be discovered within the cluster (since at least one was found from test scans of the cluster with a pre-DASCH commercial scanner) and can be follow up with archival ROSAT and other data to derive system properties. Since M44 is nearly on the ecliptic, a search will be conducted for asteroids or other high proper motion objects. The high galactic latitude (33deg) of the field and large number of mag. 14-15 galaxies included on each plate will permit a search for historical supernovae.

## 2005 Interns

INTERN: Jennifer Blum (Columbia University)

PROJECT TITLE: Stellar Rotation
ADVISOR: Dr. Andrea Dupree
MENTORS: Jeno Sokoloski

ABSTRACT:
The He I 10830{\AA} line in the spectra of cool luminous stars, can reveal the dynamics of the chromosphere because the line-forming process is independent of local conditions. Following photoionization of neutral helium by the star's X-ray and EUV flux, helium recombines into a metastable state. Thus, absorption in the He I line serves as an excellent tracker of the mass outflow leading to mass loss. Using high resolution spectra from the Fourier Transform Spectrograph on the Canada-France-Hawaii telescope (CFHT) and the SOFIN echelle spectrograph on the Nordic Optical Telescope (NOT), we analyze the presence and strength of the He I $\lambda$10830 line to determine the chromospheric expansion velocity in 22 luminous cool stars of spectral types G and K. About half of the stars show absorption at outflowing velocities in excess of 100 km s$^{-1}$ which are comparable to typical stellar escape velocities at 1 R_star. For these targets we also explore the relation between the extent of He I $\lambda$10830 absorption and X-ray flux. This research was supported by the NSF REU Program at SAO.

INTERN: Laura Book (University of Illinois Urbana-Champain)

PROJECT TITLE: FU Orionis outbursts
ADVISOR: Dr. Lee Hartman

ABSTRACT:
The purpose of this project is to make time dependent calculations of simple accretion disk models with an aim toward explaining FU Orionis outbursts. These events consist of jumps in mass accretion rate by several orders of magnitude in protoplanetary disks. The large, rapid increases of mass provide significant physical constraints on the structure of pre-planetary disks that are otherwise unobtainable. The project will consist of calculating the evolution of disks with a two-zone model that allows for the effects of limited disk ionization on the magnetorotational instability and a parameterized version of angular momentum transport by gravitational instability. The results of these calculations will be used to construct light curves to compare with observations.

INTERN: Krzysztof Findeisen (Cornell University)

PROJECT TITLE: AGN Heating of Galaxies and Groups
ADVISOR: Dr. Paul Nulsen
MENTORS: Ryan Hickox

ABSTRACT:
X-ray observations with the Chandra satellite have shown that large amounts of energy can spew from supermassive black holes, also called active galactic nuclei (AGN), at the centers of large galaxies. The energy emerges from AGN in pairs of opposing jets and gets deposited in the surrouding region. In the massive elliptical galaxies and groups of galaxies that have atmospheres of hot X-ray emitting gas, the energy inflates cavities in the gas. The plasma inside the cavity often emits at radio wavelengths, so we see a 'radio lobe' inside it. In some cases Chandra has also detected shock fronts (like sonic booms) that surround the cavities, created when the cavities are inflated with explosive speed.

The energy injected into the gas by this process has a major effect on the hot gas. Without it, the gas should have cooled long ago to form stars, so it probably has a large effect on the process of galaxy formation. By measuring the energy we can also infer how rapidly the supermassive black holes grow. We would like to know how often this happens, how much energy is injected, and whether it happens in all galaxies. These questions can be answered in part by doing a survey of nearby galaxies and groups of galaxies from the Chandra archive to find cavities. From the size of a cavity and the pressure of the surrounding gas, we can determine the energy required to make it. By seeing how common they are, we can estimate how frequently they occur and how much energy they pump into the gas.

INTERN: Conrad Hutchenson (University of Arizona)

PROJECT TITLE: IR Properties of Galaxies in Clusters and Groups
ADVISOR: Dr. John Huchra
MENTORS: Nathalie Martimbeau

ABSTRACT:
The 2 Micron All-Sky Survey is the source of a major new catalog of galaxies with well measured photometric properties in the near infrared. Distances/redshifts have now been measured for a complete sample of ~24,000 galaxies from this catalog and morphological types have been estimated for almost all the galaxies.

We will complete the visual classification of the remaining 10% of the sample and use this complete survey to study the global properties of the galaxies in the sample, including color versus morpological type, color versus luminosity, the interal extinction in spiral galaxies from color versus inclination.

If time permits, we will also study differences in galaxy properties as a function of their environment. The major scientific question is to understand how the process of galaxy formation depends (or not, as the case might be) on environment by clearly measuring the how global properties change versus such parameters as the local galaxy density and the depth of the potential wells (galaxy clusters) in which they form.

INTERN: Harrison Prentice-Mott (University of Pennsylvania)

PROJECT TITLE: Cryogenic X-ray Detector Laboratory
ADVISOR: Dr. Eric Silver
MENTORS:

ABSTRACT:
The student will learn about broad band , high resolution x-ray and gamma-ray detectors that are being developed for use in space- and ground-based applications. These include fundamental physics measurements of highly charged ions produced in heavy ion accelerators and laboratory plasmas; 2) spectroscopic measurements of cosmic x-ray

and gamma ray sources such as black holes, supernova remnants and clusters of galaxies; 3) industrial and medical applications where high resolution x-ray spectroscopy is important to materials and chemical analysis. The intern will participate in laboratroy experiments associated with improving the performance of these instruments and thereby learn low temperature and solid state physics and how to to do spectroscopic analysis. There are several specific , self-contained projects that the intern will be able to concentrate on and present to the group at the completion of his/her internship.

INTERN: Michael Rutkowski (Hampden-Sydney College)

PROJECT TITLE: The Supernova Remnant E0102-72
ADVISOR: Dr. Eric Schlegel
MENTORS:

ABSTRACT:
E0102-72, a remnant in the Small Magellanic Cloud, has a circular shape with 'spokes' connecting back to the center. It shows strong emission lines of oxygen and because of this emission, it has been used to monitor the increasing absorption layer on the ACIS detector on Chandra. That means there is a large quantity of data on this object available in the data archive. This project will extract the best of the data, those pointings closest to the optical axis of the telescope, and sum them to (1) search for a point source of emission; (2) search for time-dependent motion in the rim. The second is particularly interesting: over approximately 6 years of observations, the reverese shock has been moving all that time. It may be detectable in the SE portion of the remnant where a sharp rim exists.

INTERN: Shannon Schmoll (University of Washington)

PROJECT TITLE: A Search for Asteroids in the EXPLORE Project Dataset
ADVISOR: Dr. Gabriela Mallen-Ornelas
MENTORS: Dr. Matt Holman

ABSTRACT:
The currently accepted theory for the formation of planetary systems postulates that terrestrial planets formed by the collisional growth of kilometer-sized rocky bodies known as planetesimals. Asteroids are leftover relics from this phase in the history of the Solar System. It is believed that the asteroid belt contains objects of different origins, ranging from planetesimals to fragments of planet embryos. The size distribution of asteroids is critical for understanding their collisional history.

The goal of this project is to identify and characterize a sample of faint asteroids in images from the EXPLORE search for transiting extrasolar planets. The EXPLORE database consists of thousands of images of 3 fields taken every 2-3 minutes over a period of 1-2 weeks per field. The images were taken with CCD mosaic cameras on the CTIO and KPNO 4m telescopes and the 3.6m CFHT. These observations constitute a unique dataset in terms of depth and time sampling of the observations and will therefore lead to a sample of main belt asteroids fainter than those in most existing studies. Moreover, it will be possible to produce light curves on the discovered asteroids, leading to a period measurement for the fastest rotators.

Asteroids can be found in difference images created as a by-product of the search for transiting planets. Difference images are produced by subtracting a template image from each frame, thus leaving a mostly empty frame, with only time-variable and moving objects remaining. The student will find the asteroids, calculate their orbital elements (by modifying existing computer programs), produce a luminosity function for the sample, create light curves, and interpret the results.

INTERN: Megan Schwamb (University of Pennsylvania)

PROJECT TITLE: Applications of Gravitational Lensing: Light Curve Studies
ADVISOR: Dr. Rosanne Di Stefano
MENTORS:

ABSTRACT:
One way to detect and study masses lying between us and a distant bright source field is to study light curves that may contain evidence of gravitational lensing by these masses. A new generation of observing programs is being planned. We will carry out some theoretical studies that can serve as input to the design of these programs, optimizing their potential to study dark matter, and also to teach us about local stellar remnants.

The focus of the project can be guided by the interests of the student. We could concentrate on simulations of specific source fields, on the search for MACHOs, on the study of binarity through monitoring observations, or on the search for planets.

INTERN: Paul Sell (University of Toledo)

PROJECT TITLE: High-redshift Galaxies Study
ADVISOR: Dr. Matthew Ashby
MENTORS: Dr. Jia-Sheng Huang

ABSTRACT:
The Spitzer Space Telescope is the fourth and final great observatory and has created entirely new opportunities to study and better understand objects in the distant, early universe. This is owing to a combination of its unprecedented sensitivity in the mid-infrared (3-10 microns) and its privileged position in a novel earth-trailing orbit, where the celestial backgrounds are very low and even thermal emission from the earth is minimi zed.

We are seeking a motivated student to work with Spitzer imaging data to attempt to detect elusive nascent galaxies at redshifts of z=4 using a version of the now well-established dropout technique. The project is organized into three phases.

The first phase involves collecting and reducing optical broadband data at the KPNO 4 m Mayall telescope with the MOSAIC wide-field camera. Drs. Ashby and Huang will be traveling to Kitt Peak to acquire these data (four nights have already been granted for this purpose, June 9-12), and we would hope the student would join us for that observing run so as to gain real hands-on experience with at a world-class astronomical facility (they have funding to pay your expenses if it fits into your schedule). The reduction portion of this work would involve standard processing of the imaging data acquired at KPNO, various quality assessment tasks, and the generation of a catalog of sources in the resulting combined images.

The second phase of the project will entail value-added' analysis to the catalog. Among other things, the catalog would be combined with an existing catalog of sources detected by IRAC, and searched for objects that are visible to IRAC but only weakly detected or not detected at all by the MOSAIC camera. Such optically-faint infrared-bright objects will form the basis of a sample of candidate high-redshift galaxies.

The third phase will be a check on the validity/feasibility of the selection technique. Existing spectroscopic redshift databases can be examined for overlap with the sample, and photometric redshift techniques c an also be applied as proof-of-concept.

Completion of the first two phases of the work alone would certainly be worthy of a AAS poster presentation, and we expect that the student should be able to accomplish those and possibly most or all of the third portion in the 9 or 10 weeks available. The first two phases constitute the primary objective of the student's work. We would hope, however, that the student would be able to make significant contributions in the third phase, and woule want to be involved in subsequent proposals that we plan in order to follow up on the most promising sources spectroscopically. That portion of the plan would require a large-aperture observatory and would not of course be possible on the short timescales of the summer work period. It would nonetheless give the student further scope for work in this field if he/she were interested in building on the experience.

INTERN: Sarah Sonnett (College of Charleston)

PROJECT TITLE: Spitzer/IRAC Photometry of T Dwarfs
ADVISOR: Dr. Brian Patten
MENTORS: Dr. Massimo Marengo

ABSTRACT:
The Spitzer Space Telescope is one of NASA's Great Observatories. One of the three science instruments on board Spitzer is the Infrared Array Camera (IRAC), a four channel camera that uses two pairs of 256x256 pixel InSb and Si:As IBC detectors to provide simultaneous images at 3.6, 4.5, 5.8, and 8 microns. With the goal to define the IRAC colors for brown dwarfs, we have acquired photometry for some ~80 stellar and sub-stellar mass objects with spectral types of late-M, L and T. Our data shows that the T dwarfs stand out from the other brown dwarfs in IRAC colors, and provide the most insight into the nature of brown dwarf atmospheres. In particular, we find that the T dwarf photometry and colors do not agree entirely with the predictions of theoretical models, suggesting there is a second parameter, other than temperature, that one must consider. The most likely candidate is mass, since sub-stellar mass objects cool continuously after their formation. Among objects with similar spectral type, the range of mass suggested by our sample is from about 15 to 70 Jupiter masses.

Because our original GTO sample was designed to sample as wide a range of spectral types as possible, with a only a few representatives for each spectral type bin, we need to expand our sample size of T dwarfs to better test how observation compares to theoretical modeling for these objects. An additional sample of T dwarf data has been acquired under the Nearby Stars GTO program for this purpose.

The student will reduce and analyze IRAC images for about a dozen relatively nearby brown dwarfs. The student will become familiar with the IRAC camera and how the data were taken with this space-based instrument. Software developed locally will be used to produce cosmic-ray-cleaned, co-added data from multiple exposures of the same object. Routines in IRAF will be used to extract the photometry for the objects of interest from each field. These new data will be combined with existing data for late-M, L, and T dwarfs, to better investigate the preliminary conclusions we have drawn from the data analyzed thus far about T dwarfs in the solar neighborhood.

## 2004 Interns

INTERN: Ryan Anderson (University of Michigan)

PROJECT TITLE: Spitzer Imaging of Young Stellar Clusters: Surveying Star Forming Regions for Disks and Protostars
ADVISOR: Dr. Tom Megeath
MENTORS: Drs. Lori Allen, Phil Myers

ABSTRACT:
How do stars form? In the last thirty years we have learned that 1.) stars form in cold molecular clouds, 2.) that stars form not in isolation, but in clusters, and 3.) that most stars form with circumstellar disks - these disks are the progenitors of solars systems like are own. However, there is still much to learn. The fact that stars form in dense clusters raises the possibility that interactions between stars may govern the process of star and planet formation. For example, disks may be destroyed in dense clusters by radiation and dynamical stripping, thus preventing the formation of planets.

Studying the formation of stars and early evolution of protoplanetary disks requires sensitive infrared observations. The recently launched Spitzer Space Telescope is already providing such data on star formation. One of the three instruments on board Spitzer, IRAC - Infrared Array Camera, was built at the CfA. In return, we now have over 800 hours guaranteed time observations. Almost 100 hours of this time is being dedicated to surveys of star forming regions, including a survey of young stellar clusters and the Orion Molecular clouds. Spitzer has been taking science observations since the beginning of December, and we are now collecting a growing gallery of star forming regions. Each one of these star forming regions is a snapshot of the cluster forming process, by obtaining many snapshots covering a range of ages and environments, we hope to disentangle the complex feedback mechanisms which may occur in these regions.

As a project, the student will be assigned a star forming region in the Orion molecular cloud containing a cluster of young stars. Using Spitzer data, the student will identify stars with disks and protostars in this cluster, and compare their region with other star forming regions in our database.

INTERN: Debarati Chattopadhyay (Lehigh University)

PROJECT TITLE: Imaging the Solar Corona with the Solar Dynamics Observatory (launch 2008)
ADVISOR: Dr. Mark Weber
MENTORS: Alana Sette

ABSTRACT:
The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics Observatory (launch 2008) will provide images of the whole solar corona in 8 passbands (8 different temperatures) every 10 seconds, 24 hours a day for five years. This project will involve the development of tools to analyze the AIA data stream efficiently. One of the computationally intensive jobs is to compute the "differential emission measure" (DEM) of the corona from the AIA data sets. The DEM defines the amount of plasma at each temperature along the line of sight in the image. We will create simulated images of the corona (from a set of 3-D computations) and process those images to reconstruct the DEM at each point in the image. Parallel processing techniques will be applied with the goal of estimating the computation time required for a full set of 16-Megapixel AIA images.

In addition, the student will help us evaluate the effectiveness of different DEM image display options, including single temperature emission maps and time-progression DEM movies.

INTERN: David (Clay) Hambrick (Harvey Mudd College)

PROJECT TITLE: Shock Heating of Cooling Flow Clusters
ADVISOR: Dr. Paul Nulsen
MENTORS:

ABSTRACT:
X-ray emission that reveals the hot intergalactic gas in clusters of galaxies also carries away its heat. Near to the center of many rich clusters, the rate of heat loss is sufficient to cool the gas to low temperatures many times over since the cluster was formed. These are known as cooling flow clusters. Despite the heat loss, observations with Chandra and XMM-Newton show that little of the gas does cool significantly, so that some heat source must make up for the radiative losses.

Chandra observations have also shown that radio sources at the centers of many cooling flow clusters have inflated large cavities in the X-ray emitting gas. When these "bubbles" rise buoyantly through the gas, their energy (enthalpy) is converted to heat in their wakes. This form of heating is substantial, but insufficient to replace radiative losses in most cases. Recently, weak shocks, driven by the expanding radio lobes, have also been detected surrounding the radio lobes in several systems. In each of the three cases analyzed so far, the energy of the shocks is more than adequate to make up for the radiative losses from the cooling flow. In two of them the energy is significant for heating the whole cluster, showing that shock heating by active galactic nuclei could play a significant role in the overall energetics of clusters of galaxies.

Depending on interests, a student will do some of the following: search the Chandra archives for more examples of shocks generated by expanding radio lobes; analyze Chandra data for a system of shocks to determine their basic physical properties, particularly age and total energy; investigate the histories of energy input to the shocks, subject to the observed constraints, especially preservation of abundance gradient.

INTERN: Cecelia Hedrick (University of Nebraska)

PROJECT TITLE: Outbursts in Symbiotic Binary Stars
ADVISOR: Dr. Jennifer (Jeno) Sokoloski
MENTORS:

ABSTRACT:
Symbiotic stars are binary star systems in which a red-giant star and a white-dwarf star orbit one another. Since the red giant is very large and puffy, the material at the stellar surface is only gravitationally bound to the rest of the star very loosely. The strong radiation field from the red giant can therefore push the material away in a wind. The companion white dwarf has a very strong surface gravitational field, and it captures a portion of the red-giant wind as it passes by. In some cases, the accreted material forms a disk around th white dwarf.

Observationally, symbiotic binary stars can suddenly brighten in the optical, and then slowly fade. But the cause of these 'outbursts' is not well understood. They could be due to an instability in the accretion disk around the white dwarf, a change in the rate of nuclear burning on the surface of the white dwarf, expansion of the white-dwarf photosphere, or some combination of all of these effects.

We have been collecting weekly optical brightness measurements of five interesting X-ray-bright southern symbiotic stars. The goal the intern's project will be to examine these data and 1) see if we have found any new outbursts, 2) analyze any new outbursts in an attempt to constrain physical mechanisms, and 3) generally characterize the optical variability properties (including searching for periodic variations which could be associated with the orbital motion) of these five systems.

INTERN: Tyrel Johnson (University of Idaho)

PROJECT TITLE: Development and Fabrication of Magnetic Microcalorimeter Detectors for Future Space Missions
ADVISOR: Dr. Susanne Romaine
MENTORS: Dr. Ricardo Bruni

ABSTRACT:
We are currently collaborating with GSFC, Brown University and NIST (CO) to develop magnetic microcalorimeter detectors for use in future X-ray astromony space missions.

The proposed project will involve the student in the fabrication and characterization of materials and devices which is necessarily an interdisciplinary experience. Several areas including: physics, astronomy, materials science and engineering are applicable in this project.

INTERN: David Myer (University of California San Diego)

PROJECT TITLE: X-ray Emission from E/S0 Galaxies
ADVISOR: Dr. Eric Schlegel
MENTORS:

ABSTRACT:
E/S0 galaxies essentially have 2 components to their X-ray emission: point sources (read: X-ray binaries) and diffuse emission from hot gas. The point source emission scales with the blue optical luminosity; the diffuse emission appears to follow a different relation. The low-luminosity E/S0s (L_B < 10.5) are expected to be devoid of diffuse emission, yet several show considerable quantities of hot gas.

Archival Chandra observations of a few low-luminosity E/S0 will be analyzed to extract the diffuse emission. The spatial distribution will be extracted and fit with an appropriate profile function. Fit values will be correlated with E/S0 galaxy parameters to examine the role of the expected dominant contributors (mass, age, etc.). One model, for example, implies that the X-ray surface brightness profile should depend on the wind state of the galaxy.

INTERN: Joseph Neilsen (Kenyon College)

PROJECT TITLE: Pulse Profiles and Phased Spectroscopy of SMC X-1
ADVISOR: Dr. Saeqa Vrtilek
MENTORS: Dr. Bram Boroson

ABSTRACT:
Data: 8 roughly 8ksec observations with Chandra Acis-S in CC mode. 4 obs. during X-ray High State and 4 obs during X-ray low state of the roughly 60 day superorbital period.

SMC X-1 is part of a massive X-ray binary system with 0.7 second pulses. It is one of only two known sources to show both pulses and bursts. It is also the only X-ray pulsar for which no spin-down episodes have been observed. This suggests that SMC X-1 has a magnetic moment that is an order of magnitude lower than those of typical X-ray pulsars. Observations with less sensitive instruments suggest that the pulse profile changes dramatically between high and low X-ray states. ACIS-S in CC mode is ideal for determining pulse profiles and conducting pulse phased spectroscopy. We have determined the pulse period with great accuracy from this data. However, it is important to conduct a systematic study of pulse profile as a function of orbital phase, superorbital phase, and energy.

INTERN: Megan Roscioli (Haverford College)

PROJECT TITLE: Morphologies of mid-infrared galaxies
ADVISOR: Dr. Pauline Barmby
MENTORS: Dr. Matthew Ashby

ABSTRACT:
Galaxies detected at mid-infrared wavelengths are believed to be important contributors to the total star formation in the universe, and thus to the cosmic infrared background. Yet the nature of these galaxies -- dusty elliptical galaxies, star-forming spirals, or train-wreck' mergers -- has remained elusive because of the small areas and limited spatial resolution of previous mid-IR surveys. We how have a huge sample of mid-infrared galaxies from a survey done with the IRAC instrument on the Spitzer Space Telescope. Combining this with a published catalog of morphological parameters measured from Hubble Space Telescope observations of the region will help in the understanding of the nature of this population of galaxies.

INTERN: Krystal Tyler (Purdue University)

PROJECT TITLE: AGN Activity in Nearby Galaxies Detected at Infrared Wavelengths With the Spitzer Space Telescope
ADVISOR: Dr. Michael Pahre
MENTORS: Dr. Giovanni G. Fazio

ABSTRACT:
The new Spitzer Space Telescope provides unprecedented spatial resolution and sensitivity for studying the properties of nearby galaxies in the mid- to far-IR. The goal of this project is to try to detect AGN activity in several dozen nearby galaxies -- of a wide range of morphological types and luminositie s - -- imaged at 3 < lambda < 160 um with Spitzer. The AGN will be identified in two different ways: (1) spatially, by fitting 1-D/2-D models to the light distributions, thereby looking for a point source in the nucleus; and (2) by looking for nuclear regions significantly redder than the inner bulges, via 1-D surface brightness profiles. The sensitivity to AGN activity measured by these methods will be estimated using simple, 2-D model galaxy simulations. The AGN detections/fluxes will be compared to Chandra X-ray Observatory data, either through literature searches or by analysis of archival data (where appropriate) . They will also be compared to the nuclear activity measured for the sample via optical spectroscopy, as documented in the literature (e.g., Ho, Filippenko, & Sargent 1995, 1997, ...).

INTERN: Iris Monica Vargas (University of Puerto Rico)

PROJECT TITLE: Exploring the Playground of the Nucleus: Characterizing the Nuclear Extended Emission in Chandra's Early-Type Galaxy Sample
ADVISOR: Dr. Christine Jones

ABSTRACT:
A sample of 19 galaxies from the O'Sullivan catalogue was selected and further categorized according to velocity dispersion values and the extent of their X-ray emission using data from the radial emission distribution profiles made with funtools/DS9 applications. Galaxies were grouped into eight sets, with velocity dispersion values ranging from low velocity dispersion values 54-74 km/s) to high velocity dispersion values (190-300 km/s) and observed extended emissions in the range of 7-340 arcseconds. Data from the observations were processed and spectra were fitted by XSPEC. Fluxes were obtained for all objects as well as other figures of merit such as temperatures and luminosities. It was determined that the obesrved X-ray extended emission in the low-luminosity early-type galaxies of our sample, is in the scale of a few kiloparsecs and appears to be dominated, in general, by a gas component rather than by unresolved point sources.

INTERN: Linda Watson (University of Florida)

PROJECT TITLE: Study of Stellar Atmospheric Structure and Distance Estimation using a UV-optical Interferometer in Space
ADVISOR: Dr. Margarita Korovska
MENTORS: Drs. Dimitar Sasselov, Massimo Marengo

ABSTRACT:
Direct imaging of stars other then the Sun is crucial for understanding the structure of stellar atmospheres, their activity and magnetic fields, and the variability driven by processes such as periodic pulsation. Surface details cannot be resolved using current ground- and space-based telescopes and interferometers even for nearby giant and supergiant stars. We are currently exploring the possibility of imaging atmospheric structures and studying the pulsation processes in a set of variable stars including Cepheids and evolved giants and supergiants using a long-baseline UV-optical interferometer such as the Stellar Imager (SI). The Stellar Imager is expected to have a ~500m baseline and will produce images with ~0.1 milliarcseconds angular resolution. SI represents an advance in resolution of at least two orders of magnitude when compared to the HST and will thus be an invaluable resource for many areas of astrophysics, including understanding stellar activity, stellar magnetic fields, and for estimating cosmological distances.

This project will concentrate on studies of the potential for interferometric imaging of pulsating atmospheres and stellar surface structures at UV-optical wavelengths. The work will involve simulations of a Cepheid atmospheres and of surface brightness distribution, taking into account the hydrodynamic effects associated with the pulsation processes and will use results from numerical simulations of red giant convection structures to carry out interferometric imaging simulations.

Work Description: The student will run existing software to produce models of surface brightness distributions for a set of cases, and will run a simulator to produce images as seen by the SI interferometer. A summer intern will also carry out diagnostics studies of the stellar activity and variability using the results from these simulations.

## 2003 Interns

INTERN: Cassandra Fallscheer (California Polytechnic San Luis Obispo)

PROJECT TITLE: A COMPLETE Search for Young Stellar Outflows
ADVISOR: Dr. Alyssa Goodman
MENTORS:

ABSTRACT:
One way to identify active star formation is to search for molecular outflows, because they have been observed toward protostars in high frequency. Outflows are an important source of turbulence in star-forming molecular clouds, and they inject significant amounts of energy into the surrounding medium.

The COMPLETE Survey of Star-Forming Regions (cfa-www.harvard.edu/COMPLETE) will provide the perfect database for an outflow search. COMPLETE is comprised of COordinated Molecular Probe Line Extinction and Thermal Emission observations of three large star-forming regions scheduled to be extensively observed by SIRTF. What is unique about COMPLETE is its coordinated approach. Prior observations of the types Included in COMPLETE abound, but they only rarely fully-sample any region, and no survey has ever covered a single (~10 pc) region fully with molecular line, extinction, and dust emission observations. The lack of an unbiased survey like COMPLETE has left star formation theories without statistical constraints on the temporal and spatial frequency of: inward motions, outflow motions, star formation; cloud disruption; core formation and several other key parameters.

Using the COMPLETE molecular line maps taken at FCRAO, a summer intern should be able to search for molecular outflows and make an important contribution to the field of star formation.

INTERN: Wesley Fraser (McMaster University)

PROJECT TITLE: Outer Planet satellites
ADVISOR: Dr. Matt Holman
MENTORS:

ABSTRACT:
Unavailable.

INTERN: Joleen Miller (Villanova)

PROJECT TITLE: Extrasolar planets
ADVISOR: Dr. Pete Nisenson
MENTORS:

ABSTRACT:
Direct imaging of extra-solar planets or planetary systems would provide coarse photometric and spectroscopic information, giving insights into the planet's atmospheric composition. It would also give an unambiguous determination of the planet's mass (if combined with radial velocity data) by eliminating the ambiguity in the orbital inclination. Direct imaging is extremely difficult due to the large dynamic range required to separate the light from the central star from the light reflected by the nearby planet. Both the diffraction from the telescope aperture and scattered light need to be controlled with extreme precision for planet imaging.

We have a program (partially supported by an NSF grant) to test a concept for achieving the very high dynamic range required for detection of reflected light from exo-planets. We will use an Apodized Square Aperture (ASA) (Nisenson and Papaliolios, 2001) to control the telescope diffraction. ASA adjusts the transmission of the telescope pupil and dramatically reduces diffraction by the telescope except along two narrow crossed, on-axis strips, perpendicular to the edges of the aperture. ASA was originally conceived to be used, in the visible, in NASA's Terrestrial Planet Finder mission as an alternative to an infrared interferometer for finding and characterizing terrestrial-sized extra-solar planets. In this program, ASA could also be used, when combined with adaptive optics and speckle techniques, to detect the light from optimally placed giant planets (orbits known from radial velocity measurements) orbiting nearby stars.

We are currently setting up to perform lab simulations that allow us to test our cameras, apodizing technique, and data analysis algorithms. A summer intern could help us take test data, help develop the software for data analysis (using IDL), analyze the simulation data, and even help us write a paper on the results. This will prepare us for observing runs using these techniques that will start next fall.

INTERN: Michael Mortonson (Massachusetts Institute of Technology)

PROJECT TITLE: X-ray detector development
ADVISOR: Dr. Eric Silver
MENTORS:

ABSTRACT:
I am interested in offering a summer project to an intern interested in experimental physics. The intern will learn about low temperature physics and cryogenic techniques applicable to the development of high resolution x-ray detectors. This may include traveling to the National Institute of Standards and Technology (NIST) to participate in laboratory astrophyiscs measurements on an Electron beam Ion Trap. I will have a better idea of the exact project once I meet with the student.

INTERN: Chris Orban (University of Illinois Urbana Champaign)

PROJECT TITLE: X-ray stars in open clusters
ADVISOR: Dr. Brian Patten
MENTORS:

ABSTRACT:
For this project, X-ray sources will be identified and net source counts will be extracted in eight ROSAT HRI images in the regions of the NGC 2232 and Cr 140 open clusters. These X-ray data will be combined with ground-based photometry and spectroscopy in order to identify candidate G, K, and early-M type members of these clusters.

At present, no members later than about F5 in spectral type are currently known for either cluster. With ages of about 25 Myr and at a distance of just 320 to 360 parsecs, the late-type memberships of the NGC 2232 and Cr 140 clusters will yield an almost unique sample of solar-type stars in the post-T Tauri/pre-main sequence phase of evolution.

The data generated by this project will be used to bolster the late-type membership of these clusters (crucial for the study of the evolution of magnetic dynamo activity in young solar-type stars) as well to re-assess the likely ages and distances of these clusters.

INTERN: Nada Petrovic (University of Chicago)

PROJECT TITLE: Microlensing
ADVISOR: Dr. Rosanne DiStefano
MENTORS:

ABSTRACT:
Microlensing is an exciting tool to probe for dark matter, to study binary stars, and, potentially, to discover distant planets. The project we would work on this summer would have 2 possible components: (1) comparing different microlensing techniques to discover planets, and (2) to study the influences that source and lens binarity have on estimates of the optical depth. The optical depth is a measure of the amount of dark matter that may be in the form of compact massive halo objects (MACHOs).

INTERN: Dan Perley (Cornell University)

PROJECT TITLE: Search for galaxy clusters
ADVISOR: Dr. Paul Green
MENTORS:

ABSTRACT:
Unavailable.

INTERN: Caroline Ring (University of North Carolina Greensboro)

PROJECT TITLE: Infrared star forming regions
ADVISOR: Dr. Lori Allen
MENTORS:

ABSTRACT:
This August the NASA SIRTF telescope system is due to launch, and it is expected to discover thousands of very young stars in the nearest star-forming complexes by observing at mid-infrared wavelengths. To prepare for our group's observing programs with this telescope, we want to assemble complementary near-infrared observations of our target regions, made in the last several years with the ground-based 2MASS telescope. These data have just been released, and are easily accessible over the internet. This program is an opportunity for a student to make a comprehensive study of the stellar content of nearby star-forming regions, and to learn useful techniques of data analysis.

INTERN: Paul Taylor (Boston College)

PROJECT TITLE: Small Magellanic Cloud
ADVISOR: Dr. Andreas Zezas
MENTORS:

ABSTRACT:
With Chandra we can obtain very sharp images of other galaxies. This allows us to probe their X-ray source populations to much fainter limits than was possible before. We chose to observe one of our nearest star-forming galaxies, the Small Magellanic Cloud, in order to study its low luminosity X-ray sources. The main aim of this project is to detect the discrete sources in the five fields of our SMC survey and perform a preliminary study of their X-ray properties (hardness ratios and possibly variability by comparison with earlier ROSAT and Einstein source lists). In a later stage these results will be used to produce an X-ray luminosity function of these sources. Comparison with results from other galaxies studied at this depth (eg Milky Way, M33, M31) as well as with other more distant galaxies will be used to understand the relation between star-formation activity and X-ray source populations. The SMC has been extensively observed in the optical so we will be able to identify optical counterparts of the X-ray sources by cross-correlating them with lists of optical sources.

A student who will work on this project will learn how to analyze X-ray and optical data using existing and previously tested software (CIAO, Sherpa, IRAF). There are ready made scripts and tasks to do parts of this analysis which will be used by the student (after of course the required training). They will also be exposed to the interpretation of scientific data and learn about the different types of sources in galaxies and how we can distinguish between them using observations in different wavebands (mainly optical and X-rays). This way they will learn about the current views of the connections between galactic X-ray source populations and stellar populations. Finally they will learn how to do background literature research on a specific topic.

INTERN: Deborah Turner-Bey (Rockhurst University)

PROJECT TITLE: Magnetism in A-type Stars
ADVISOR: Dr. Vinay Kashyap
MENTORS:

ABSTRACT:
To explore the limits of magnetic dynamo activity on stars at the high-mass end of the the main sequence. The magnetic dynamo begins to operate for late A type stars and is the cause of coronal X-ray emission. No early type A stars have been detected in X-rays, and the location of the boundary where magnetic activity (and hence coronal X-ray emission) turns on has been an open question for decades. Observations with Chandra provide a means to attack this problem. Starting from optical catalogs of bright blue stars and then searching through the ChaMP database to determine whether these stars have been detected or whether upper limits must be set on the flux, we can study the onset of magnetic activity and coronal emission on normal stars.

INTERN: Katherine Whitaker (University of Massachusetts Amherst)

PROJECT TITLE: X-rays from Cluster Abell 119
ADVISOR: Dr. Ralph Kraft
MENTORS:

ABSTRACT:
We will study the X-ray emission from the nearby (z=0.0442) cluster of galaxies Abell 119 using archival XMM-Newton data. Previous optical and X-ray observations suggest that this cluster is undergoing a minor merger. We will use the X-ray data to determine the temperature, the pressure, and the elemental abundances of the gas. From this we will be able to compute the total gravitating mass (i.e. dark matter) in the cluster. We will also create a temperature map to search for evidence of structures related to the merger. Such phenomena include 'cold-fronts', possible 'abundance-fronts', and shocks. The scientific goal of this project is to better understand the hydrodynamics of cluster mergers and the formation of structure.

Abstracts for end-of-summer talks

1)   Cassandra Fallscheer (CalPoly/San Luis Obispo)

The study of molecular outflows is very important in the quest for understanding the process of star formation. Using data collected in the Coordinated Molecular Probe Line Extinction Thermal Emission (COMPLETE) Survey, a list of known molecular outflows in the Perseus Cloud Complex was compiled. A process was developed to search the COMPLETE data for new candidates of molecular outflows.

2)   Wesley Fraser (McMaster University)

Pencil Beam Search Technique and the Size Inclination Distribution of the Kuiper Belt

In this paper we discuss a new technique of finding moving objects in a series of images. this technique implements a 'shift and add' method of stacking images, and allows a deeper probing than the standard three image detection routine. We describe the results of using this technique on an ecliptic Kuiper belt survey. We use this and three other ecliptic surveys to analyze the possibility of different size distributions for the high and low inclination objects. We find it highly likely (99%) that there is only one size distribution between the two groups.

3)   Joleen Miller (Villanova)

Calculating Velocity Shifts Between the Pre- and Post-Upgrade AFOE Data Sets

We present the results of our efforts to develop a procedure to determine the velocity shifts between the stellar reference spectra before and after the upgrade of the Advanced Fiber Optic Echelle (AFOE). When the AFOE spectrograph was upgraded to increase its ability to measure radial velocity variations, the change necessitated taking new stellar references for each star system. All velocity measurements for a given star are made relative to this reference, which is simply an observation of the star on a particular night. However, there is an unknown velocity shift between every pair of new and old stellar reference spectra simply because they were observed on different nights. In addition, other intrinsic differences between the two spectra prevent us from simply recalculating all of the velocities relative to one reference or the other. To overcome this problem, we have begun developing a procedure that calculates the velocity shift between a pair of new and old stellar references. We perform the calculation independently for each wavelength range of the new spectrum that overlaps the old spectrum, which gives us twelve measurements of the velocity. The spread in our results gives us an idea of the precision of our calculations, and we hope to be able to measure the velocity shift with a precision of ~ 1m/s. In this paper we explain our procedures in more detail and discuss our progress of calculating the velocity shift for the star beta Aquilae.

4)   Michael Mortonson (MIT)

Commissioning a New X-ray Microcalorimeter for Laboratory Astrophysics

We have completed a new X-ray microcalorimeter system to detect X-rays from plasmas produced by an Electron Beam Ion Trap at the National Institute of Standards of Technology. the instrument is an upgrade to a detector that was previously used for laboratory astrophysics; it has a 1x4 array of microcalorimeter detectors and improved cooling and data acquisition capabilities. During the test run of the new instrument, spectra of highly charged ions of neon, argon, and krypton were obtained and calibrated using observations of X-rays from a calibration target. We report on the data and the performance of the instrument, noting its advantages over the previous detector as well as a few new technical problems that must me addressed.

5)   Chris Orban (UIUC)

Late-type Membership in the Open Cluster NGC 2232

NGC 2232 is one of the nearest open clusters (~360 pc) with an age of ~25 Myr. This places it in the unique position to study the transition from T Tauri activity to the Zero Age Main Sequence. In order for those studies to begin, late-type members must be identified for the clusters. X-ray observations combined with ground-based photometry and spectroscopy offers the best way to accomplish this goal. We present photometry in the VRI bands, 2Mass near-infrared measurements in the J, H, K bands and spectra for the suspected optical counterparts to the X-ray sources in the field of NGC 2232. 46 late-type members were identified through these efforts.

6)   Nada Petrovic (University of Chicago)

The Role of Binary Sources and Binary Lenses in Microlensing Surveys of MACHOS

Microlensing is a fascinating phenomenon which both provides a confirmation of the General Theory of relativity as well as yields information about the portions of our galaxy that we cannot see, such as dark matter. early microlensing observational searches located strong candidates of point lens, point source light curves as well as binary source and binary lens light curves. However, very few mildly perturbed light curves were observed, which a problematic omission. Also, Di Stefano has suggested that the failure to take binary effects into account may have influence`d the estimates of optical depth derived from microlensing surveys. This paper is a first step in a systematic analysis of binary lenses and binary sources and their impact on statistical microlensing surveys. In order to begin assessing this problem, we ran large-scale Monte Carlo simulations of various microlensing events involving binary stars (both as the source and as the lens) in order to study the lensing and perturbation rates. The five situations we focussed on were a point lens/point source case, the point lens/binary source without binary motion, point lens/binary source with binary motion, binary lens/point source, and a binary lens/binary source including binary motion. For each lensing event we recorded the parameters of the system as well as the times where the curve reached 1.34 magnification. We also sampled the characteristic light curve and recorded the chisq value of a point lens fit to this light curve as will as the maximum magnification. Finally, we recorded the numbers of repeating events, or events which temporarily dipped below the 1.34 magnification value. Using the recorded parameters for each system we were able to reconstruct our sampling range for each individual value of closest approach in order to directly compare the lensing rates in all five of the cases. We found that the binary source light curves had a lensing rate approximately 1.04 times the rate of the point source/point lens light curves. On the other hand, the binary lens light curves had a rate of approximately 1.4 times the rate of the point lens/point source case. Using the chisq values for the fits, and defining a chisq of greater than 1.5 to be perturbed, we found the perturbation rate of binary source light curves to be approximately 5-6% and the perturbation rate due to binary lenses to be approximately 32% which increased to 35% with addition of a binary source to the binary lens. We found significant rates of repeating events in all cases but the point source/point lens. The point lens/binary source with motion, and the binary source/binary lens case had significant fractions of repeating events with more than one repeat, while the binary lens point source and the binary source with no motion mainly caused events with one repeat. We used the starting and ending times of the curves to determine the duration rates of the various lensing events. We noted that the durations were slightly different for each of the five simulations, and that the binary lens cases tended to have a larger fraction of short duration events. Finally, we used the maximum values of the sampled curves to calculate the distance of closest approach as it would be calculated by observers, noting that in the binary lens case an artificially high number of events appeared to have small distances of closest approach due to the high magnifications caused by caustic crossings.

7)   Dan Perley (Cornell University)

Explorations in Multiwavelength Cluster Detection Using Chandra

In this project, we search for serendipitous X-ray clusters, investigate their properties and assess their detectability in optical surveys. Using automatic and manual methods, we search 62 Chandra observations retrieved from archival data in ChaMP, the Chandra Multiwavelength Project, for extended sources. We use visual inspection and red_sequence analysis to evaluate these sources, isolating possible new clusters from spurious detections and non-cluster sources. In addition to detecting five previously known sources, we find two new probable clusters and one additional cluster candidate. Cluster detections are analyzed to estimate redshifts, X-ray luminosities, and other information. We also investigate the Voronoi Tessellation and Percolation (VTP) algorithm in combination with red sequence-based color filtration as a potential cluster finding tool. In preliminary tests, we find that filtered VTP successfully detects all seven (primarily optically faint) clusters in the sample to which it is applied, but a large number of apparently spurious sources are also detected that would have to be screened out via color-magnitude analysis or another confirmatory method. Early results are very encouraging, but further investigation will be needed to establish the practical effectiveness of the algorithm in optical cluster detection.

8)   Caroline Ring (University of North Carolina at Greensboro)

An Examination of Starless Molecular Cloud Cores in SIRTF Core-to-Disks Sample

The SIRTF Legacy Cores-to-Disks (c2d) program has compiled a database of molecular cloud cores planned for observations using SIRTF. Cores in the c2d sample have not been examined for star formation using a uniform database since IRAS (launched 1983). We use the 2MASS database to examine the c2d sample of molecular cloud cores which have been classified as "starless" for infrared excess sources, which, if found, would imply that their classification whould be changed. (J-H) - (H-K) color-color diagrams are used to identify sources with infrared (IR) excess. IR excess sources whose projected position lie within the boundaries of the molecular cloud cores are examined further, using spectral energy distributions, in an attempt to classify them.

9)   Paul Taylor (Boston College)

A Chandra Survey of the Bar Region in the Small Magellanic Cloud

We present the results of a survey of the central part of the Small Magellanic Cloud Galaxy by the Chandra X-ray Observatory. The field of view covered an area of 1280 square arcmin along the most active region of the SMC with five observations between May and October, 2002. This survey was performed with ACIS (Advanced CCD Imaging Spectrometer) in an energy range 05.-0.7 keV. Sources were detected using the wavdetect algorithm, and then spectral and timing analyses were performed on bright detections. the survey yielded a total of 122 significant sources (at 3 sigma level) down a flux near 1e-14 erg/sec/cm2 in the full band (0.7-1.0 keV) and near 1e-15 erg/s/cm2 for the soft band (0.1-2 keV). Among these sources we identify two supernova remnants, seven known X-ray binaries, and eight sources which are most likely pulsar binaries, based on spectra and variability from the Chandra data. Log(N)-Log(S) relations were used to compute the number of detected sources not associated with the SMC region, and that value was found to be at most 155 sources, with a minimum of ~50 sources. Comparisons were made with previous X-ray and optical surveys for identification of sources, namely the ROSAT PSPS and HRI, ASCA, and UBVR surveys, and then cross-correlated with the SIMBAD database. In all, 18 ASCA sources, 26 PSPC, 15 HRI and 38 UBVR were associated with Chandra sources. Due to the high density of optical sources, the probability of chance overlap was calculated and found to be ~30 sources.

10)   Deborah Turner-Bey (Rockhurst University)

The Onset of Magnetic Dynamo Activity in A-Type Stars

A solar type magnetic dynamo is believed to come into operation in late-A stars. Because coronal activity is strongly dependent on the presence of a magnetic dynamo, X-ray emission is a tracer of this dynamo. We have carried out a systematic search for A type stars in Chandra observations using the database of serendipitous detections derived from the Chandra Multi-wavelength Project (ChaMP). No X-ray emission has been conclusively detected in early-A stars, and the ChaMP database provides a significant opportunity to constrain the onset of the dynamo in main sequence stars. In this preliminary survey, we have identified numerous X-ray sources as A star candidates, and find that the data are consistent with main sequence stars becoming X-ray emitters at V-R ~ 0.15, between A6 and A9.

11)   Katherine Whitaker (UMass at Amherst)

An XMM-Newton Study of the X-ray Emission from Abell 119

We have analyzed archival XMM-Newton data of the nearby cluster of galaxies Abell 119 (A119), studying the X-ray emission from the intracluster medium. Using the beta model, derive the luminosity to be 1.64e+44 ergs/s at a radius of 0.73 Mpc, with a central density of 1.63e-3g/cm3. The total gravitating mass within a radius of 0.73 Mpc is 3.76e+15 solar masses, with a plasma mass of 3.11e+14 solar masses, giving a ratio on 8.3%. We measure the average temperature of A119 to be 5.99 keV. A temperature map and azimuthally symmetric profile with the beta model has a minor merger in the northeast region, believed to be falling in at a temperature of 4.41+/-0.44 keV along one of three filaments in the cluster.

# 2002 Interns

Ten Interns worked here during the summer of 2002.

 Student School Advisor(s) Mentor(s)* Mia Bovill University of Maryland Tyler Bourke Peter Sollins Richard Cool University of Wyoming Eric Silver Anil Dosaj Robert Friedman Rutgers University Rosanne DiStefano Ken Rines Alex Hill Oberlin College John Huchra Nathalie Martimbeau Holly Manness Grinnell College Saeqa Vrtilek Mike Raley Joannah Metz University of Illinois at Urbana-Champaign Marc Kuchner Brant Robertson Emily Alicea-Munoz University of Puerto Rico Andrea Dupree Jason Aufdenberg Anandi Salinas University of Texas at Austin Eric Schlegel Eli Beckerman Tristan Smith University of Chicago Suzanne Romaine Ricardo Bruni Daniel Wik University of Ohio Paul Green John Silverman

# 2001 Interns

Ten Interns worked here in 2001

 Student School Advisor(s) Mentor(s)* Stephanie Campbell Purdue University Nancy Brickhouse Ken Rines Adrienne Erickcek Princeton University Matt Holman Anil Dosaj Elizabeth Leass University of Texas at Austin Tom Megeath Beth Biller Samuel Vazquez Melendez University of Puerto Rico Ralph Kraft Tabetha Hole Shawn O'Brien University of Notre Dame Edwin Bergin Shanil Virani Shinae Parks University of California at Berkeley Scott Kenyon John Grimes Annika Peter University of Washington Andreas Zezas, Giuseppina Fabbiano Alceste Bonanos Nick Stroud University of Wisconsin at Madison Robert Cameron, et al.* Dave Morris Glen Nixon Purdue University James Phillips Warren Brown Adria Updike Smith College Amy Winebarger Kathy Reeves

*with Tom Aldcroft, Margarita Karovska and Dimitar Sasselov.

# 2000 Interns

Eleven Interns worked here in the summer of 2000.

 Student School Advisor(s) Mentor(s)* Deborah L. Freedman Princeton University Jan Vrtilek Shanil Virani and Laura Grego Mark Kramer Oberlin College Jim Moran and Q. Zhang Jim Moran and Todd Hunter Julia M. Kregenow Wittenberg University Ralph Kraft Amy Winebarger and Christine Jones Emily M. Laubacher University of Dayton Eric Silver Dale Graessle Nicholas Pearson Bowling Green State University Steve Saar Peter Challis Jennifer Posson-Brown Smith College David Latham Pauline Barmby Brant Robertson University of Washington Larry David Kris Eriksen Shanna Shaked University of Arizona Jonathan McDowell Dave Morris Daniel Joseph Sherman University of Pennsylvania David Bersier Kris Stanek Sabrina Zoe Siloti University of Oklahoma Eric Schlegel Ken Rines Fernando Angel Torres University of California at Davis Hank Donnelly Tabetha Hole

*Anil Dosaj will act as "mentor at large" for all of the interns.

# 1999 Interns

Project Descriptions

Summer Lecture Series

 Student School Advisor Mentor Alceste Bonanos Wellesley College Peter Garnavich Deron Pease Carolyn Ernst Brown University Matt Holman Olivia Johnson Francisco Galvan Colby College Mike Garcia Kris Eriksen/Vicky Kalogera (Co-mentors) Erik Hoversten Iowa State Nuria Calvet Ray Jayawardhana Vit Hradecky California Institute of Technology Christine Jones Hank Donnely Naibi Marinas University of Florida Jim Phillips Priya Desai John Moustakas University of California at Berkeley Eric Schlegel Anil Dosaj Margaret Pan Massachusetts Institute of Technology David Latham Malin Ljungberg David Rothstein Haverford College Paul Ho Dave Wilner David Smith University of Texas Kenneth Wood Kenneth Rines Heidi Tebbe University of Missouri Brian Patten Alexandria Ware Kathryn Whitman Cornell University Brian McNamara Laura Grego

# 1998 Interns

 Student School Advisor Mentor Marianne Vieira Univ. of Rochester Jim Babb N. Balakrishnan Catherine Slesnick NYU Bob Donahue, Sallie Baliunas (Co-advisors) Jacqueline Chen Yale University John Huchra Brian McNamara Meghan Novicki Univ. of Michigan Christine Jones-Forman Hank Donnelly Robert Cohen Univ. of Idaho Steve Murray Martin Zombeck, Ralph Kraft, Almus Kenter Micol Huw Christopher Harvard Univ. Phil Myers Lori Allen, James di Francesco, Tom Megeath Colleen Schwartz Colby College Suzanne Romaine John Everett/Ric Bruni Gregory Herczeg Univ. of Notre Dame Steven Saar Adrian Daw Michael Baird Grove City College Eric M. Schlegel, Peter Garnavich Ken Rines Beth Lindsey Bryn Mawr Dave Wilner Qizhou Zhang

# 1997 Interns

 Name Undergraduate Institution Project Titles James Chisholm Northwestern University Identification of Selected Einstein Slew Survey Sources with the ROSAT HRI Rebecca Danos Wellesley College Calculation of the Cosmological Deceleration Constant from Clusters of Galaxies Michael Dorris Vanderbilt University Redshift-Magnitude Relations for Galactic Clusters Lynne Raschke Haverford College Chromospheric Variations in Post Main-Sequence Stars Brian Rebel Grinnell College M31: It's Not Where You Left It Eric Rosolowsky Swarthmore College Analyzing Molecular Clouds Using the Spectral Correlation Function Alicia Soderberg Bates College Type Ia SN1997E in NGC 2258: UBVRI Photometry and a Multicolor Light Curve Shape Distance Analysis Jesse Southwick Princeton University Multilayer Fabrication and Characterization Using Auger Spectroscopy Jason Wright Boston University An Analysis of the Evolutionary State of the SNR G299.2-2.9 Using ASCA and Optical Data

# 1996 Interns

 Name Undergraduate Institution Project Titles Avanti Athreya Iowa State University The Reception of Kepler's Astronomia Nova and an Analysis of his Rudolphine Tables Alison Coil Princeton University Infalling Gas Toward the Galactic Center Nate Emley University of Massachusetts, Amherst Spectroscopic Orbits for White Dwarf Binaries Identified Andrew Frey Wake Forest University An Infrared Survey of Protostars in the Perseus Molecular Cloud Becca McMullen Whitman College Forward Modeling of Coronal Flows Julia Plummer Washington State University ROSAT X-ray Imaging of Hot Gas in Galaxy Clusters Yelena Prok University of Virginia Search for Black Hole X-ray Binaries Ken Rines Rice University Temperature Distribution of Distant Galaxy Clusters from ASCA Richard Scalzo University of Virginia Strategies for Discovering Planetary Systems Using Gravitational Microlensing Alice Shapley Harvard University The Infrared Region of Radio-Quiet Quasar Spectral Energy Distribution Aaron Sokasian Cornell University Characterization and Fabrication of Multilayers

# 1995 Interns

 Name Undergraduate Institution Project Titles Dave Bacon Cal Tech The Viability of a Two-Photon Mechanism by Molecular Hydrogen or Ionied Molecular Hydrogen as an Explanation fof the Diffuse Interstellar Absorption Bands Kenneth Banas University of Michigan The Association of Supernova Remnants and Molecular Clouds in the Large Magellanic Cloud Lara Cross Trinity University The Shapes of Clusters of Galaxies Within Superclusters Ben Lane Cal Tech Improved Mass Determination of the Soft X-ray Transient A0620-00 Wendy Lane Rice University A Search for Redshifted H I 21 cm Absorption by Damped Ly Alpha Absorption Systems Jennifer Lotz Bryn Mawr Optical Structure in the Zwicky 3146 Central Cluster Galaxy Rob Simcoe Princeton University Axial Ratio Statistics of Soft X-ray Selected Low Redshift AGN Stephen Stanec Case Western Reserve The Dependence of Microchannel Plate Energy Resolution on Photocathode Microstructure Rachel Theran University of Michigan Clusters of Galaxies and X-ray Binaries in the Einstein Slew Survey Beth Wicklund Tufts University Low Resolution IUE Observations of Chromospheric Mg II h and k Emission Cherie Willoughby University of Massachusetts Black Holes

1994 Interns

 Name Undergraduate Institution Project Titles John Everett Carleton College AXAF X-ray Reflectivity Measurements of Iridium coated Witness Samples Lisa Falkson Stanford University Discovering Dwarfs: Infrared Photometry of Dwarf Carbon Stars Natasha Hazell Fordham University The Distribution of Dark and Luminous Matter in Elliptical Galaxies Eran Jones Southwest Missouri State Compilation of Emission Line Equivalent Widths of QSOs and AGNs Nicole Lloyd Cornell University Thermal X-ray Emission from Neutron Stars Travis Metcalfe University of Arizona The Low-Mass Double-Lined Eclipsing Binary CM Draconis Kendra Michaud University of Maine Heavy Metal Abundance in Eliptical Galaxies Nicholas Putnam Brown University Pulsar Parallaxes and Proper Motions with VLBI Ali Thomas Morehouse College Matching of X-ray and Optical Sources Heather Thompson University of Arizona A Search for X-ray Substructure in Cooling Flows Steven Vance Andrews University Applications of Multiresolution Filtering and Deconvolution using Wavelets Jenny White Howard Agnes Scott College The Luminosity Distribution of Low Mass X-ray Binaries in the Galactic Bulge Amy Winebarger University of Tennessee A Brief Study of the Corona Surrounding a Specific Sunspot Region

For more information about the research divisions at the Harvard-Smithsonian Center for Astrophysics, see the CfA Home Page.

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The photo below was taken at the 2014 AAS meeting, and shows SAO interns from years as far back as 1997, and many members of our 2013 class.