Are Gas-rich Field Ultra-diffuse Galaxies and Dwarf Galaxies Distinct Populations?

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Authors

Motiwala, Khadeejah

Date

2024-09-12

Type

thesis

Language

eng

Keyword

galaxies , dwarf galaxies , ultra-diffuse galaxies

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Abstract

Over the past decade, significant developments in instrumentation and image searching techniques have uncovered thousands of low surface brightness objects that were previously uncatalogued. Among these are ultra-diffuse galaxies (UDGs) - objects that represent the extremes of galaxy properties. UDGs have stellar content similar to classical dwarf galaxies, but physical sizes more akin to Milky Way-type galaxies; as such, several theories for how UDGs may form differently from dwarfs have been proposed. In this thesis, we aim to constrain the different formation mechanisms in two ways. First, we compile and present the largest catalogue of optically-selected field UDGs and dwarfs with distance measurements in the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) catalogue. We compare the UDGs and dwarfs in SMUDGes to investigate whether UDGs are a distinct population. Second, we compare the SMUDGes observations with two state-of-the-art cosmological simulations: NIHAO (Numerical Investigation of a Hundred Astrophysical Objects), which forms UDGs through bursts of star formation at early times and Romulus25, which forms UDGs from major mergers. Although formation scenarios for UDGs with these simulations are remarkably different, the present-day, global properties of the simulated galaxies are consistent with our observed sample. Furthermore, in both simulations and observations, we find no distinct difference between the UDGs and classical dwarf populations within the gas-richness vs size parameter space. The results presented in this work include the first detailed study of gas-rich UDGs in both observations and simulations.

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