2013 IPAC Visiting Graduate Fellowship

Program Description

The Infrared Processing and Analysis Center (IPAC) at Caltech announces the availability of six-month graduate student fellowships. The program is designed to allow students from other U.S. or international institutions to visit IPAC-Caltech and perform astronomical research in close association with an IPAC scientist. Eligible applicants are expected to have completed preliminary course work in their graduate program and be available for research during the period of the award. Funding from IPAC will be provided for a 6-month period via monthly stipends, plus relocation expenses. Several students are expected to be accepted each year, subject to the availability of funding. Students are expected to be at IPAC during the duration of the Fellowship, nominally January to July, with some flexibility on the starting and ending dates.

Description of Research Projects

Reverberation Mapping of Circumstellar Disks Around Young Stars

Advisor: Peter Plavchan

This project will involve a student to reduce and analyze time-series photometry of young stars. The project will exploit data from the Spitzer Space Telescope and other facilities. The science goal of the project is to detect a time lag between emission from a protostar and its surrounding circumstellar material, and to use the finite speed of light to directly measure the distance between the star and circumstellar material. Dr. Plavchan is interested in both the formation and frequency of planets around M dwarfs and has discovered young stars with circumstellar disks that exhibit long-term periodic variations in their brightness. Several other related projects can be considered, including the reduction and analysis of radial velocity data. Experience with coding, UNIX, and basic astrophysics is desired.

Probing Known Exoplanets for Possible Transit Signatures

Advisor: Stephen Kane

Transiting planet discoveries have yielded a plethora of information regarding the internal structure and atmospheres of extra-solar planets. Monitoring known radial velocity planets at predicted transit times is a proven method of detecting transits, and presents an avenue through which to explore the mass-radius relationship of exoplanets in new regions of period/periastron space. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) provides a vast dataset through which to investigate these planets for possible transit signatures. The student will have an opportunity to work with exoplanet photometry and radial velocity data and investigating the properties of eccentric planets.

Investigating the Relationship Between Planetary Orbits and Habitable Zones

Advisor: Stephen Kane

The exoplanet field is entering a realm where studies of exoplanet characterization and habitability are increasingly accessible. The rate of exoplanet detection, particularly in potentially habitable zones, is steadily increasing. This project presents a unique opportunity for a student to work with experienced exoplanet hunters and habitability experts in a synergistic environment. The student will perform upgrades to the Habitable Zone Gallery (HZG) from which new planetary systems may be investigated. The result of this work will be an enhanced HZG and new science results for habitable candidates and their atmospheres. The direct science question being addressed is: What is the frequency, size distribution, and orbital dynamics of planets within the Habitable Zone?

Star formation Along the Coma Supercluster

Advisor: Dario Fadda

This project will use recently released WISE data in conjunction with archival GALEX images and SDSS DR9 images and spectra to study how the specific star formation rate of galaxies is affected by the environment along the filament connecting the Coma cluster to the A1367 cluster. Several galaxy groups are known to exist along the filament and this project will explore how star formation and morphology of galaxies are affected by the location of the galaxies and their distance from the centers of the two clusters. The student will perform accurate photometry with in-house software of the galaxies belonging to the filamentary structure using at the same time archival images in the optical, infrared, and UV bands and will study the morphology of the galaxies using SDSS images. Star formation rates, stellar masses, morphological and spectral classifications will be derived for each member and related to the position along the filament and the density of the environment. This study on a nearby system with multi-wavelength coverage will shed new light on the processes involved in the evolution of galaxies travelling along filaments towards rich clusters.Experience in treatment of images in the UNIX/IDL environment is welcomed.

The Formation of Massive Red-End Sequence Galaxies

Advisor: Vandana Desai

It has long been recognized that galaxies follow a basically bimodal color distribution, often termed the red sequence and the blue cloud. The red sequence is comprised of galaxies with little or no star formation, while the blue cloud consists of actively starforming galaxies. This project is aimed at understanding the formation of the bright (massive) end of the red sequence. We will measure the merger activity among luminous red galaxies within the cores of ten galaxy clusters at redshifts in the range 0.5 < z < 0.8. These measurements will allow us to test whether today's most massive galaxies could have assembled a significant fraction of their stellar mass via major dry (gas-free) mergers since z = 1, as has been suggested in the literature. The cluster sample is drawn from the ESO Distant Cluster Survey (EDisCS), and is well-characterized with data from many facilities, including groundbased optical and near-infrared imaging, optical spectroscopy, HST morphologies, and Spitzer imaging. The data products are well-established, and the student would work with reduced images and data tables. This is a well-defined project that would feasibly lead to a publication during the timeframe of the program. Basic programming skills are necessary.

Frozen Polycyclic Aromatic Hydrocarbons

Advisor: Adwin Boogert

Polycyclic Aromatic Hydrocarbon molecules (PAHs) are the source of prominent infrared emission bands, ubiquitously observed in Galactic and extragalactic star forming regions as well as evolved stars. As these vibrational bands are excited by ultraviolet (UV) radiation, little is known about PAHs in low-UV environments such as in molecular clouds and circumstellar disks and envelopes. Yet in these regions, PAHs may have a profound impact on the chemical evolution as they are an important reservoir of elemental carbon. It is expected that they freeze out on grain surfaces together with CO, H2O, CH3OH, CO2, etc. So far, frozen PAHs have not been detected, largely due to the unknown band positions, widths, and intrinsic strengths. For this reason we have measured the absorption spectra of laboratory analogs of several interstellar PAH species frozen in H2O ice. We are looking for a student to analyze the laboratory spectra and subsequently compare them with available infrared spectra of Young Stellar Objects and dense clouds. Experience with IDL or another plotting and line fitting package is preferred.

Abundances of Late-Type Stars in the Galactic Center

Advisor: Solange V. Ramirez

The Galactic Center is one of the most exciting places in the Galaxy. It is a region where old and young populations coexist in an environment that is actively forming stars. This project is aimed to address the issue of selective enrichment between iron-peak and alpha elements in late-type stars within 50 pc of the center of our Galaxy, and hence understand if the Galactic Center Initial Mass Function (IMF) is skewed towards massive stars. Abundances will be determined using observed high-resolution infrared spectra (taken with PHOENIX at Gemini) and synthetic models generated by MOOG. Interest in stellar spectroscopy and experience with coding is desired.

A Study of the mid/far-IR Properties of the Interstellar Medium (ISM) Around the Eagle Nebula and M16
Advisors: A. Noriega-Crespo (IPAC/Caltech), N. Flagey(JPL/Caltech), R. Paladini (NHSC/Caltech) & S. Carey (SSC/Caltech)
We are looking for a student with interest in ISM studies of gas and/or dust, IR imaging and spectroscopic data to further expand the recent study of Flagey et al. 2011 (A&A, 531, 51) on the Eagle Nebula/M16. The Eagle Nebula is one of the best known regions in the Milky Way and has been the focus of a wealth multi-wavelength studies. The proposed project will help us to characterize the dust and gas emission properties of the nebula based on the analysis of a spectral map obtained with the Infrared Spectrometer (IRS) on board the Spitzer Space Telescope over an approx. 23x27arcmin field. This data will be complemented with broad band imaging from the GLIMPSE, MIPSGAL, HiGAL and WISE surveys.

Dynamical Modeling of Luminous Infrared Galaxy (LIRG) Mergers Hosting AGN

Advisors: Joseph Mazzarella, Steve Lord & Lee Armus

The Great Observatories All-sky LIRG Survey (GOALS) is combining imaging and spectroscopic data from numerous space-borne and ground-based observatories in a comprehensive study of 200 of the most luminous infrared-selected galaxies in the local Universe. One of the primary objectives is to characterize the variation of nuclear star formation and AGN properties as a function of the host galaxy properties. A key factor is understanding the evolutionary stage of the host galaxies during the merger process. For this project, the candidate would focus on matching dynamical models to a small number of merging LIRG systems that have a rich set of suitable multi-wavelength data. The resulting models will be used to study nuclear activity as a function of merger stage. A candidate with experience in applying N-body/SPH code (e.g., GADGET; Springel & Hernquist 2002) and Identikit test-particle techniques (Barnes & Hibbard 2009) would be best suited for this study, which requires matching simulations of the stellar and gas dynamics with the observed morphological, photometric, and kinematic information. A related project of mutual interest proposed by the candidate may also be considered, but should be designed so it is feasible to submit a journal article describing the results by the end of the program period (or soon after).