Hydrodynamic simulations of galaxy formation in a cosmological context

Abstract

The formation of galaxies and their subsequent evolution through cosmic time is governed by a variety of complex physical processes such as gas cooling, star formation, feedback and merger events. In this thesis we use hydrodynamical simulations to study the effect of these processes on galaxy properties. We first investigate the change in galaxy morphology as they undergo mergers. We look at a wide variety of merger events from interaction between small dark matter subhaloes and galactic discs, to major mergers. In the second part of the thesis we turn our attention to the role of stellar feedback in regulating star formation. A model for short range photoheating of gas by radiation from massive stars is tested by simulating a representative volume of the Universe and comparing the statistical properties of simulated galaxies with the observed ones. Finally, we introduce a new, computationally efficient model to calculate the gas cooling rate in the presence of local radiation fields. The model uses simple assumptions for absorption of ultra-violet photons and an optically thin approximation to propagate local radiation fields throughout the entire simulation volume. Using this new method we show that local radiation has a significant effect in regulating the star formation rate of L* galaxies. It reduces gas accretion onto the disc, thereby, producing realistic galaxies without resorting to extreme feedback mechanisms.