Environment provides a potentially powerful, and under exploited, test for models of galaxy evolution. This thesis explores the use of environment through the study of two physical processes, ram pressure stripping and major mergers. As a satellite orbits through the hot inter-cluster or inter-group medium, its cold gas can be stripped. The effectiveness of ram pressure stripping depends on the group environment, making it an ideal candidate for an environmental study. To examine this dependence an analytical model is developed which can be applied to a wide range of host group and satellite masses and can therefore easily be placed in a cosmological context. The implications of this model are explored, and the model is then confronted with observations of galaxy group members in the Sloan Digital Sky Survey. A strong correlation is observed between galaxy color and group mass. This correlation is not predicted by other models of galaxy evolution, but can be understood as the effect of ram pressure stripping.
Current cosmological models predict that mergers between galaxies are common. Major mergers are an extreme class of merger in which the morphology of the galaxies involved is severely disrupted. Correlations between the major merger rate and environment are explored using the Millennium Simulation , a cosmological gravitational N-body simulation. The Millennium Simulation combines a large volume, which includes the full range of environments, with the mass resolution necessary to track the merger histories of the dark matter halos that typically host galaxies. The simulation results guide a physical understanding of the major merger rate as arising from the interplay between cosmology, which sets the accretion rate of halos, and the interactions of bound substructures, or subhalos, with the host halo and with each other. Inelastic scattering between subhalos plays a strong role in determining the merger rate by driving subhalos into the center of the host. The observational implications of the simulation results are briefly considered. The goal of this study is to provide the theoretical background necessary for using environment to test major merger driven models of galaxy evolution.
|Advisor:||Spergel, David N.|
|School Location:||United States -- New Jersey|
|Source:||DAI-B 69/07, Dissertation Abstracts International|
|Keywords:||Galaxy evolution, Major mergers, Pressure stripping|
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