Semi-Analytic Model Predictions of Mass Segregation from Groups to Clusters

TL;DR

This study uses high-resolution simulations and semi-analytic models to analyze galaxy mass segregation in groups and clusters, highlighting dynamical friction as the main driver and examining the effects of various physical processes.

Contribution

It provides new insights into the physical mechanisms behind galaxy mass segregation, especially emphasizing the role of dynamical friction and the limited impact of stellar stripping and post-accretion growth.

Findings

Mass segregation observed up to the virial radius in groups and clusters.

Dynamical friction is the primary mechanism driving mass segregation.

Low-mass galaxies do not significantly alter the overall mass segregation trend.

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 $M_* = 10^9 \, M_{\odot}$, 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 "anti-mass 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 onto which accreting material is falling.