Simulations of galaxy clusters

Abstract

Galaxy clusters are the largest virialised objects in the present-day Universe. Clusters are complex systems which can be used as a cosmological probe as they trace the large-scale mass distribution, but they also incorporate non-gravitational processes which make them excellent tests of galaxy formation and evolution. Due to the extremely complex nature of galaxy clusters, numerical simulations are increasingly important in order to test and understand all the different astrophysical processes that are involved in galaxies and galaxy clusters, which can be informed by and compared to observations. In this thesis, we have used the low resolution CELR sample to produce more evidence for a mass dependence of the hydrostatic mass biass, which increases from around 20 per cent to 40 per cent in the most massive objects. It is important to understand and characterise this bias in order to use clusters for cosmology. We have also looked at the metallicity distribution of the C-EAGLE clusters and found that, in general, the cluster outskirts are compatible with the early enrichment model. The C-EAGLE clusters show considerable evolution in the core as a result of accretion of low metallicity gas, suggesting that active galactic nuclei have a bigger impact on metals in cluster cores than has previously been seen. Finally, we have designed and tested a module to reduce the distribution of gas particle masses in cosmological simulations to preserve the underlying smoothed particle hydrodynamics which assume a constant particle mass. This module was successfully implemented in the EAGLE cosmological code, but was unable to stop the formation of entropy cores in clusters.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Neal Jackson (Supervisor) & Scott Kay (Supervisor)