Star formation activity and gas stripping in the Cluster Projected Phase-Space (CPPS)

This work is focused on the study of the distribution in the Cluster Projected Phase-Space (CPPS) of passive(ly-evolving) and star-forming galaxy populations and also, the intense and quiescent star-forming populations for a set of nine nearby z < 0.05 galaxy clusters. Furthermore, we compare the CPPS distribution of the passive galaxy population with the accreted halo population of a set of 28 simulated clusters and the star-forming population with the non-accreted population. We consider various cluster accretion epochs and accretion radii, where it is assumed that star formation in galaxies becomes quenched, in order to segregate the accreted population from the non-accreted population. Just applying this segregation in simulations, we get a qualitative agreement between the CPPS distributions of the passive and the accreted populations and also between the star-forming and the non-accreted populations. The uncertainty in cluster centring strongly affects the pronounced cuspy profiles of the projected density and also, it can explain the main difference (i.e. inner slope) between the CPPS distribution of passive and accreted populations. The CPPS density of star-forming galaxies and the intensity of ram-pressure stripping present an opposite trend throughout the CPPS. This implies that ram-pressure stripping significantly contributes to modulate the observed CPPS distribution of star-forming galaxies in cluster virial regions and their surroundings. The significant fraction of star-forming galaxies at the projected centre of clusters are mainly those galaxies with low line-of-sight velocities and they can be mainly identified as those galaxies with a remaining star formation activity (quiescent star-forming galaxies) inside the physical virial region or, in a lower degree, as galaxy interlopers, i.e. outside the physical virial region. This paper also includes a test of the effects caused by the Sloan fibre collision on the completeness of the Main Galaxy Sample as a function of cluster-centric radius.