Characterizing Dwarf and Diffuse Galaxy Populations in the Local Universe

Abstract

Extragalactic astronomy in the last decade has greatly benefited from significant improvements to (1) astronomical instrumentation and (2) data reduction and analysis techniques. These improvements afford the ability to reveal ever fainter low surface brightness (LSB) dwarf galaxies at optical wavelengths. Thoroughly characterizing these dwarf galaxies is essential in furthering our understanding of how galaxies form and evolve. Accordingly, there have been several concerted efforts to compile and characterize the properties of (1) satellite dwarf galaxies around Milky Way-like systems beyond the Local Group and (2) a subset of large, LSBs known as Ultra-Diffuse Galaxies (UDGs) whose properties fall at the extreme end of the dwarf galaxy population. In this thesis, I will present studies that aim to illuminate both of these sub-fields by exploiting their neutral hydrogen (HI) gas and star-forming properties. The first of these studies focus on the HI gas content of LSB dwarf galaxy satellite candidates around the nearby spiral, M101, with the aim of obtaining spectroscopic distance estimates to them via their HI content and investigating any potential environmental trends related to their HI content. The second study compares the quenched and star-forming satellite populations from the Satellites Around Galactic Analogs (SAGA) survey to two state-of-the-art zoom-in hydrodynamical simulation suites, APOSTLE and Auriga, in order to understand the relatively low observed quenched satellite fraction. The second half of this thesis presents an extensive HI follow-up survey of optically-detected UDG candidates from the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey. This follow-up survey aims to confirm SMUDGes UDG candidates as bonafide UDGs by obtaining spectroscopic distances estimates and to place constraints on their formation mechanisms using their HI properties.