Formation and Evolution of
Galaxy Clusters Across Cosmic Time

We quantify the relative importance of environmental quenching versus pre-processing in z~1 clusters by analysing the infalling galaxy population in the outskirts of 15 galaxy clusters at 0.8 We find significant differences between the infalling galaxies and a control sample; in particular, an excess of massive quiescent galaxies in the infalling region. These massive infalling galaxies likely reside in larger dark matter haloes than similar-mass control galaxies because they have twice as many satellite galaxies. Furthermore, these satellite galaxies are distributed in an NFW profile with a larger scale radius compared to the satellites of the control galaxies. Based on these findings, we conclude that it may not be appropriate to use 'field' galaxies as a substitute for infalling pre-cluster galaxies when calculating the efficiency and mass dependency of environmental quenching in high redshift clusters. By comparing the quiescent fraction of infalling galaxies at 1 < R/rv < 3 to the cluster sample (R/rv < 1) we find that almost all quiescent galaxies with masses > 1e11 Msun were quenched prior to infall, whilst up to half of lower mass galaxies were environmentally quenched after passing the virial radius. This means most of the massive quiescent galaxies in z~1 clusters were self-quenched or pre-processed prior to infall.