Semi-analytic model predictions of mass segregation from groups to clusters

Abstract

Taking advantage of a high-resolution simulation coupled with a state-of-art semi-analytic model of galaxy formation, we probe the mass segregation of galaxies in groups and clusters, focusing on which physical mechanisms are driving it. We find evidence of mass segregation in groups and clusters up to the virial radius, both looking at the galaxy stellar mass and subhalo mass. The physical mechanism responsible for that is consistent with dynamical friction, a drag-force that brings more massive galaxies faster towards the innermost regions of the halo. At odds with observational results, we do not find the inclusion of low-mass galaxies in the samples, down to stellar mass M*=109 M⊙, to change the overall trend shown by intermediate and massive galaxies. Moreover, stellar stripping as well as the growth of galaxies after their accretion, do not contribute either in shaping mass segregation or mixing the radial mass distribution. Beyond the virial radius we find an 'antimass segregation' in groups that progressively weakens in clusters. The continuous accretion of new objects and recent merger events play a different role depending on the halo mass on to which accreting material is falling.