The effects of energy injection into the intergalactic and intracluster media

This thesis presents the Millennium Gas suite of simulations - the largest cosmological hydrodynamical simulations to date - and examines the effects of different prescriptions for energy injection and radiative cooling on populations of galaxy clusters. We conclude that the dfferences between populations of clusters generated by a simulation with an epoch of preheating, and one with a continual injection of energy (feedback), are minimal at the present day (both in good agreement with observations), but that the evolution of the two populations of clusters differs. High redshift observations of cluster gas fractions suggest that continual energy injection is the preferred method. We examine possible causes of scatter in the cluster gas fraction, but are unable to determine a cause, or combination of causes, of this scatter. We combine the previously used feedback prescription with the same radiative cooling prescription as was used in the preheating simulation. Although the bimodality is not as clear as in observations, this model produces a sample containing both cool core and non-cool core clusters.