Author ORCID Identifier

https://orcid.org/0000-0002-8571-9801

Date of Award

Spring 2023

Document Type

Thesis (Ph.D.)

Department or Program

Physics and Astronomy

First Advisor

Ryan C Hickox

Abstract

Galaxy populations are shaped by the physical processes that regulate their star formation and central black hole growth throughout cosmic time. The primary aim of this thesis is to understand how these processes occur and how they shape evolution in some of the most extreme galaxies in the Universe including quasars, compact starbursts, and ultra-diffuse dwarfs. Gas-rich major mergers funnel large amounts of gas towards the nucleus, triggering rapid AGN accretion and compact star formation. In this work, I study powerful quasars and extreme, massive, compact starburst galaxies within the context of merger-driven galaxy evolution scenarios. One aim of this work was to place constraints on the nature of obscuration in AGN. Quasar clustering results suggest that obscured quasars reside in more massive dark matter halos than their unobscured counterparts. However, it is unclear if this discrepancy is tied to galaxy evolution processes, or is a result of other physical and selection effects. Here, I find that models that allow for obscuration to evolve on timescales typical of galaxy evolution are favored. Using similar modeling techniques, I also study a population of extremely compact, massive starburst galaxies that show extreme nuclear star formation and large-scale, energetic outflows. In order to make the first determination of their intrinsic space density, I construct a model population of these galaxies and assess the targeting criteria and selection effects to uncover the timescales over which these sources could be detected. The results indicate that extreme stellar feedback could be responsible for quenching a small but significant fraction of extremely star forming post-merger galaxies. Lastly, this work focuses on spectroscopy of ultra-diffuse galaxies (UDGs) with the Southern African Large Telescope (SALT). Understanding UDGs as a population could provide insight on how the faintest galaxies form and if weak stellar feedback could stunt the growth of what would be Milky Way-like galaxies. I use SALT to measure redshifts of UDG candidates to determine the effectiveness of selection techniques and add to the still small but growing known population of UDGs.

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