Exploring the history of star formation in galaxies and its environmental dependence at high redshift

The first stars formed in the early universe and shortly after assembled into the first galaxies. Since then, galaxies have been subject to a variety of processes, both internal and external, that affect their ability to form stars. At low redshift, environment plays a large role in inhibiting star formation, however it is less clear what effect it has at high redshift. This is predominantly due to the difficulty of determining the nature of the high redshift environment from uncertain redshift measurements, and the small coverage of high redshift surveys leading to poor sampling of the cosmic variance. In this thesis I use a variety of numerical approaches to various aspects of this problem. In the first section I use a semi-analytic model to study the relationship between observed galaxy surface overdensity and the probability of coinciding with a protocluster, the pre-collapse progenitors of galaxy clusters, and make recommendations for optimum measurement apertures for their identification. In the second section I use a suite of hydrodynamic simulations of galaxy clusters, across a range of descendant halo masses, to study the galaxy evolution in their protocluster progenitors in detail. I characterise the star-forming sequence, studying it’s difference in protocluster and field environments, as well as within dense groups in the collapsing protocluster. In the final section I use a novel approach to estimate the star formation history of galaxies. Rather than studying the high redshift environment directly, I estimate when the stars in a low redshift galaxy were formed using population synthesis techniques. In this work I couple this with hydrodynamical simulations in order to provide more informative priors on the shape of the star formation history, which typically imposes strong biases on inferred properties, such as the total stellar mass, in more traditional approaches.