Growing up in the city : a study of galaxy cluster progenitors at z>2

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 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.