Galaxy Mergers and Some Consequences: The Cosmological Context

The last few years have seen enormous progress in the field of galaxy formation and evolution. The latest generation of hydrodynamic cosmological simulations (e.g., the "Illustris" simulation) has been able to produce reasonably realistic populations of galaxies by tracking the evolution of dark matter, gas, stars, and black holes over a cosmological volume "representative" of the large-scale density field. However, such increasingly sophisticated cosmological simulations require equally sophisticated analysis tools. The first part of my thesis work consisted in developing a method for connecting galaxies across cosmic time, which results in data structures known as merger trees. My algorithm, known as SUBLINK, improves upon previous methods by making galaxies less likely to become "lost" during close interactions, and has been benchmarked in a merger tree code comparison project, with favorable results. The second part of my thesis work, and the main topic of this dissertation, consists of a series of essential and increasingly complex applications of my merger trees: (1) measuring the merger rate of galaxies, (2) finding out how galaxies acquire their stellar mass, and (3) investigating the impact of mergers on galaxy morphology. I will show how my analysis tools, in combination with the Illustris cosmological simulation, have made quantitative and statistically robust contributions to the field of galaxy formation and evolution, where galaxy mergers are known to play a fundamental role.Astronom