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Exploring the Extremes of Galaxy Evolution: Progenitors of Star-Forming Galaxies and Relics of Quiescent Galaxies
Abstract
In this dissertation, I investigate the formation and evolution of galaxies by studying two extreme populations — young, highly star forming galaxies (SFGs) at z > 2, and old, quiescent galaxies in the local Universe that are likely unchanged since z ≈ 2. In the first project, I use spectral energy distribution (SED)-fitting to analyze the star formation histories (SFHs) of a population of extreme emission line galaxies (EELGs) identified in the ZFOURGE Survey at 2.5 ≤ z ≤ 4, comparing them to more typical SFGs at the same redshift range. This is the first z > 2 study to use the PROSPECTOR SED-fitting code. The EELGs display rising SFHs in the most recent 50 Myr, while more typical SFGs do not. I estimate that many, if not most, SFGs at z ≥ 2.5 undergo an extreme Hβ+[OIII] emission line phase early in their lifetimes. In the second project, I present 0ʺ.14-resolution Atacama Large Millimeter/submillimeter Array (ALMA) CO(2−1) observations of the circumnuclear gas disk in the local compact galaxy UGC 2698, a member of a sample of nearby early-type galaxies that are plausible z ≈ 2 red nugget relics. I fit molecular gas-dynamical models to the ALMA data cube, assuming the CO emission originates from a dynamically cold, thin disk, and measure the mass of the supermassive black hole (BH) in UGC 2698. I explore systematics in the model and their effects on the measured BH mass. The BH in UGC 2698 is found to be consistent with the BH scaling relations, which I contrast with previous stellar-dynamical measurements for three other objects in the local compact galaxy sample. In the third project, I present ALMA CO(2−1) observations at a resolution of 0ʺ.22 in the local compact galaxies NGC 384 and PGC 11179. I make preliminary molecular gas-dynamical BH mass measurements in these galaxies and explore their systematic uncertainties. Finally, I discuss the next steps required to finalize these measurements and the implications of these results for our understanding of BH−host galaxy co-evolution and the scatter of the BH scaling relations.
Citation
Cohn, Jonathan Hall (2022). Exploring the Extremes of Galaxy Evolution: Progenitors of Star-Forming Galaxies and Relics of Quiescent Galaxies. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197785.