Probing the truncation of galaxy dark matter halos in high density environments from hydrodynamical N-body simulations

TL;DR

This study uses hydrodynamical simulations to analyze how dark matter halos of cluster galaxies are truncated by tidal forces, revealing a clear dependence on cluster-centric radius and redshift, with dark matter being more stripped than stars.

Contribution

Introduces the half mass radius as a diagnostic for dark matter halo truncation and studies its evolution with radius, redshift, luminosity, and compares with lensing data.

Findings

Dark matter halos are highly truncated near cluster centers.

Half mass radius decreases with proximity to cluster center across redshifts.

Dark matter is preferentially stripped compared to stellar components.

Abstract

We analyze high resolution, N-body hydrodynamical simulations of fiducial galaxy clusters to probe tidal stripping of the dark matter subhalos. These simulations include a prescription for star formation allowing us to track the fate of the stellar component as well. We investigate the effect of tidal stripping on cluster galaxies hosted in these dark matter subhalos as a function of cluster-centric radius. To quantify the extent of the dark matter halos of cluster galaxies, we introduce the half mass radius r_half as a diagnostic, and study its evolution with projected cluster-centric distance R as a function of redshift. We find a well defined trend for (r_half,R): the closer the galaxies are to the center of the cluster, the smaller the half mass radius. Interestingly, this trend is inferred in all redshift frames examined in this work ranging from z=0 to z=0.7. At z=0, galaxy halos in the central regions of clusters are found to be highly truncated, with the most compact half mass radius of 10 kpc. We also find that r_half depends on luminosity and we present scaling relations of r_half with galaxy luminosity. The corresponding total mass of the cluster galaxies is also found to increase with projected cluster-centric distance and luminosity, but with more scatter than the (r_half,R) trend. Comparing the distribution of stellar mass to total mass for cluster galaxies, we find that the dark matter component is preferentially stripped, whereas the stellar component remains protected by the halo and is much less affected by tidal forces. We compare these results with galaxy-galaxy lensing probes of r_half and find qualitative agreement. (Abridged)