Galaxies grow by accreting gas, which they need to form stars, from their surrounding haloes. These haloes, in turn, accrete gas from the diffuse intergalactic medium. Feedback from stars and black... Show moreGalaxies grow by accreting gas, which they need to form stars, from their surrounding haloes. These haloes, in turn, accrete gas from the diffuse intergalactic medium. Feedback from stars and black holes returns gas from the galaxy to the halo and can even expel it from the halo. This cycle of gas inflow and outflow, its impact on star formation, and the detectability of the gas outside of galaxies are discussed in this thesis. The growth of galaxies and their gaseous haloes depends strongly on their mass, the age of the Universe, and the inclusion of feedback processes, as do their physical and observational properties. Show less
Galaxy clusters are the densest large scale structures in the Universe. This makes them ideal laboratories for studying the effect of environment on the formation and evolution of galaxies. To... Show moreGalaxy clusters are the densest large scale structures in the Universe. This makes them ideal laboratories for studying the effect of environment on the formation and evolution of galaxies. To truly understand the role of environment in galaxy evolution it is essential that galaxy clusters are studied across cosmic time, back to when the Universe was still relatively young and galaxy clusters were still in the process of formation. Finding these forming galaxy clusters (or protoclusters) in the early Universe is difficult. One of the ways to do this is by looking at the environment of high-z radio galaxies. These special, very massive galaxies are often at the centre of overdensities that are expected to grow into galaxy clusters. In this thesis I have studied these protoclusters in order to determine what the nature of these structures is and how they evolve and whether there is any indication of environmental in fluence on the protocluster galaxies at such early times. I have also attempted to identify new protoclusters for future research. Show less
