Abstract

We use the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulation to trace the quenching history of galaxies in its 10 most massive clusters. We use two criteria to identify moments when galaxies suffer significant changes in their star formation activity: (i) the instantaneous star formation rate (SFR) strongest drop, Gamma(SD)(SFR), and (ii) a 'quenching' criterion based on aminimum threshold for the specific SFR of less than or similar to 10-11 yr(-1). We find that a large fraction of galaxies (greater than or similar to 60 per cent) suffer their Gamma(SD)(SFR) outside the cluster's R-200. This 'pre-processed' population is dominated by galaxies that are either low mass and centrals or inhabit low-mass hosts (10(10.5) less than or similar to M-host less than or similar to 10(11.0) M-circle dot). The host mass distribution is bimodal, and galaxies that suffered their Gamma(SD)(SFR) in massive hosts (10(13.5) less than or similar to M-host less than or similar to 10(14.0)M(circle dot)) are mainly processed within the clusters. Pre-processing mainly limits the total stellar mass with which galaxies arrive in the clusters. Regarding quenching, galaxies preferentially reach this state in high-mass haloes (10(13.5) less than or similar to M-host less than or similar to 10(14.0)M(circle dot)). The small fraction of galaxies that reach the cluster already quenched have also been pre-processed, linking both criteria as different stages in the quenching process of those galaxies. For the z = 0 satellite populations, we find a sharp rise in the fraction of quenched satellites at the time of first infall, highlighting the role played by the dense cluster environment. Interestingly, the fraction of pre-quenched galaxies rise with final cluster mass. This is a direct consequence of the hierarchical cosmological model used in these simulations.