Uncovering Mass Segregation with Galaxy Analogues in Dark Matter Simulations

TL;DR

This study uses dark matter simulations to analyze mass segregation of galaxy analogues, revealing that low-mass galaxies tend to be closer to halo centers, with trends influenced by accretion histories rather than dynamical friction.

Contribution

It introduces a simple classification method for galaxy analogues in dark matter simulations and compares subhalo distributions from different halo finders, highlighting the impact of hierarchical structures.

Findings

Mass segregation is evident at small radii within halos.

Low-mass galaxy analogues are more centrally concentrated.

Mass segregation trends are weaker or absent in massive analogues.

Abstract

We investigate mass segregation in group and cluster environments by identifying galaxy analogues in high-resolution dark matter simulations. Subhalos identified by the AHF and ROCKSTAR halo finders have similar mass functions, independent of resolution, but different radial distributions due to significantly different subhalo hierarchies. We propose a simple way to classify subhalos as galaxy analogues. The radial distributions of galaxy analogues agree well at large halo-centric radii for both AHF and ROCKSTAR but disagree near parent halo centres where the phase-space information used by ROCKSTAR is essential. We see clear mass segregation at small radii (within $0.5\,r_{vir}$) with average galaxy analogue mass decreasing with radius. Beyond the virial radius, we find a mild trend where the average galaxy analogue mass increases with radius. These mass segregation trends are strongest in small groups and dominated by the segregation of low mass analogues. The lack of mass segregation in massive galaxy analogues suggests that the observed trends are driven by the complex accretion histories of the parent halos rather than dynamical friction.