An Analysis of the Environment and Gas Content of Luminous Infrared Galaxies

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Zauderer, Bevin Ashley
Vogel, Stuart N
Luminous and ultraluminous infrared galaxies (U/LIRGs) represent a population among the most extreme in our universe, emitting an extraordinary amount of energy at infrared wavelengths from dust heated by prolific star formation and/or an active galactic nucleus (AGN). We present three investigations of U/LIRGs to better understand their global environment, their interstellar medium properties, and their nuclear region where molecular gas feeds a starburst or AGN. To study the global environment, we compute the spatial cluster-galaxy amplitude, B<sub>gc</sub>, for 76 z < 0.3 ULIRGs. We find the environment of ULIRGs is similar to galaxies in the field. Comparing our results with other galactic populations, we conclude that ULIRGs might be a phase in the lives of AGNs and QSOs, but not all moderate-luminosity QSOs necessarily pass through a ULIRG phase. To study the interstellar medium properties, we observe HI and other spectral lines in 77 U/LIRGs with the Arecibo telescope. We detect HI in emission or absorption in 61 of 77 galaxies, 52 being new detections. We compute the implied gas mass for galaxies with emission, and optical depths and column densities for the seven sources with absorption detections. To study the molecular gas in the nuclear region of LIRG Arp 193, sub-arcsecond scale angular resolution is required and a method of atmospheric phase correction imperative. We present results of a large experiment observing bright quasars to test the limitations of the Combined Array for Research in Millimeter Astronomy's Paired Antenna Calibration System (C-PACS) for atmospheric phase correction. We conclude that C-PACS improves imaging capabilities when the atmospheric calibrator is nearby (&le; 6&deg;), bright (> 1 Jy), and at moderately high elevation (> 45&deg;). We map Arp 193 in <super>12</super>CO(2-1) with CARMA, achieving 0.18'' x 0.12'' (~65 pc) resolution, and demonstrating an improvement with C-PACS. We compute a molecular gas mass of 2 x 10<super>9</super> M<sub>sun</sub> and find ~20% of the total mass is in the form of molecular gas out to a radius of 750 pc. In the inner 150 pc of the nucleus, N(H<sub>2</sub>) > 10<super>25</super> cm<super>-2</super>.