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Hello, My name is Sean Linden and I am a 5th year PhD student in the Department of Astronomy at the University of Virginia working with Dr. Aaron Evans. I am currently supported by the Grote Reber Doctoral Fellowship, working at the NRAO with Dr. Aaron Evans and Dr. Eric Murphy on "Star Formation Properties of Luminous Infrared Galaxies and Normal Star-Forming Galaxies in the Local Universe."
My primary research focuses on extragalactic astronomy looking at luminous and ultra-luminous infrared galaxies (U/LIRGs). Luminous infrared galaxies (LIRG [8-1000um] 10^11; ULIRGs 10^12) are primarily interacting or merging disk galaxies undergoing enhanced star formation and active galactic nuclei (AGN) activity. Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, disk galaxies; star-bursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, dynamically hot, elliptical galaxies, as objects representing different phases of major galaxy mergers. LIRGs are some of the most massive star-forming galaxies in the universe, and although they are rare locally, they were quite common in the early Universe. In fact, half of the energy generated since the Big Bang is thought to be light from these distant star-forming galaxies. Thus LIRGs are the perfect laboratory for studying star formation in extreme environments.
To better gauge how the merging environment influences the star formation activity in LIRGs, we must compare the star formation properties of extreme starbursts to nearby, generally isolated, normal star-forming galaxies. As such, I have joined the Herschel/KINGFISH Star Formation in Radio Survey (SFRS: PI E. Murphy), which has mapped 112 extragalactic nuclei and star-forming regions in 50 nearby (d<30 Mpc) normal star-forming galaxies in Spitzer/SINGS. By studying both samples of galaxies at high spatial resolution we can make detailed morphological and physical comparisons of individual regions of star-formation activity. Ultimately, we hope that by establishing what the key differences between LIRGs and normal star-forming galaxies are, we can build a comprehensive picture of how galaxies have evolved over the course of the universe.
The Great Observatories All-sky LIRG Survey (GOALS), is combining imaging and spectroscopic data from NASA's Spitzer, Hubble, Chandra and GALEX space-borne observatories in a comprehensive study of over 200 of the most luminous infrared-selected galaxies in the local Universe. The sample consists of approximately 180 Luminous Infrared Galaxies (LIRGs), which are systems with total infrared emission brighter than 10^11 L☉ and less than 10^12 L☉, as well as over 20 Ultra-Luminous Infrared Galaxies (ULIRGs) with luminosity of 10^12 L☉ or greater. The objects are a complete subset of the IRAS Revised Bright Galaxy Sample (RBGS), which comprises 629 extragalactic objects with 60-micron flux densities above 5.24 Jy and Galactic latitude above five degrees. The RBGS objects, all with redshifts, z < 0.088, are the brightest 60-micron sources in the extragalactic sky.
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