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The Cosmic Web, and the Role of Environment in Galaxy Evolution

The Universe, on extra-galactic scales, is composed of a vast network of structures dubbed the “cosmic web”. One of the most fundamental discoveries about the evolution of galaxies is that their properties have a dependence on their location relative to this cosmic web (i.e., their environment). However, detailed studies of the environmental dependence on galaxy evolution have been extremely challenging due to the inherent complexity of the structures on the largest scales, a plethora of techniques being used to try to map the cosmic web, and other confounding factors, such as the masses of galaxies, that also affect their evolution. In this work, we will present a technique for characterizing the environments of galaxies in the cosmic web, which is comprised of two separate, but complementary, methods that together provide a more complete measure of environment. After some introductory background in Chapter 1, we will demonstrate these mapping techniques on the Coma Supercluster, and present an analysis of the star-formation activity of about 4,000 galaxies in the supercluster environment in Chapter 2. Next, in Chapter 3 we present a greatly expanded application of our mapping techniques encompassing about 60,000 galaxies within 200 Mpc that addresses several outstanding questions from the Coma Supercluster study, and also leads to new intriguing insights into the evolution of galaxies as a function of environment. Then, in Chapter 4 we present a pilot study focusing on galaxy evolution as traced by the gas content around two galaxy clusters. We also expand upon this pilot study in Chapter 5, whereupon we examine more closely the resiliency of molecular gas content, compared to the atomic gas, to the effects of the cluster environment. And finally, in Chapter 6 we present some concluding remarks and explore some promising avenues for future study.
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