Programme by Session

The majority of galaxies are found in groups or clusters, meaning that an understanding of galaxy clusters is crucial in studying galaxy evolution, large-scale structure formation and cosmology. This work utilises The Three Hundred Project, a suite of 324 hydrodynamical re-simulations of galaxy clusters, to investigate the properties and time evolution of galaxies which are members of clusters. In particular, we focus on the ‘backsplash population’ – these are galaxies which have previously passed within the virial radius of a cluster, but now reside outside of the cluster, beyond its virial radius. We show that a significant fraction of all galaxies found in the vicinity of a cluster are backsplash galaxies, but that this fraction varies between clusters. This has important implications for observations of cluster outskirts, as galaxies within the same region may have notably different histories. For example, galaxies passing through a cluster are likely to have experienced strong ram pressure stripping, and so may have different halo gas contents to galaxies infalling for the first time. The effects of the dynamical state of a cluster on its backsplash population are also discussed.