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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Astrophysics and Astronomy | External Galaxies
Galaxies in the local Universe are characterized by blue, star-forming disk galaxies, and red, massive early-type galaxies (ETGs) whose star-formation has been quenched early in the Universe's history. The ETGs are relics of the evolutionary processes that transform galaxies over cosmic time, but currently we still lack a comprehensive understanding of their evolution. An important link in the evolution of ETGs is that the first quenched galaxies (z~2) are both the most massive, and most compact, suggesting a physical connection between high stellar density and efficient, rapid cessation of star-formation. In this dissertation, I seek insight into the formation and evolution of ETGs, in particular the physical mechanisms that quench star-formation, through analysis of their star-forming progenitors at high-redshift. First, I present a clustering analysis of rare and extreme sub-millimeter galaxies, thought to be gas-rich mergers of massive star-forming galaxies, and find that their clustering is weaker than expected for the progenitors of the massive ETGs in the center of z~0 clusters. Second, I identify a population of likely progenitors of the compact ETGs at z~2 among compact star-forming galaxies at z>3, and found that the stellar populations in these compact LBGs may be older than that of coexistent LBG that are normal in terms of mass and size (i.e. not compact). The morphologies of these compact LBG, as well as the compact ETGs at z~2, appear inconsistent with the predictions from simulations of gas-rich mergers, at least to the extent that current simulations describe real gas-rich mergers. Finally, I study the conditions in the interstellar medium of a sample of these compact progenitors using rest-frame ultra-violet spectroscopy. I find faster outflows, and large populations of metal-rich massive stars in the compact progenitors compared to normal star-forming galaxies at the same epoch and stellar mass, and present evidence that winds from these massive stars are energizing the interstellar medium of these compact galaxies. I conclude with a discussion of these findings in the context of star-formation quenching in massive high-redshift galaxies, and outline future directions which may further illuminate the nature of quenching at high-redshift.
Williams, Christina, "ON THE FORMATION AND EVOLUTION OF EARLY-TYPE GALAXIES" (2014). Doctoral Dissertations. 234.