The effects of self-interacting dark matter on the stripping of galaxies that fall into clusters

TL;DR

This study uses hydrodynamical simulations to explore how self-interacting dark matter affects galaxy stripping in clusters, revealing differences in mass loss and disruption rates compared to cold dark matter.

Contribution

It provides the first detailed analysis of SIDM effects on galaxy evolution within clusters using hydrodynamical simulations, highlighting observable differences in stellar-to-halo mass relations.

Findings

SIDM galaxies lose about 25% less mass than CDM counterparts.

One-third of SIDM galaxies are completely disrupted, versus one-fifth in CDM.

Differences in stellar-to-halo mass ratios could distinguish SIDM from CDM with strong lensing.

Abstract

We use the Cluster-EAGLE (C-EAGLE) hydrodynamical simulations to investigate the effects of self-interacting dark matter (SIDM) on galaxies as they fall into clusters. We find that SIDM galaxies follow similar orbits to their Cold Dark Matter (CDM) counterparts, but end up with ${\sim}$25 per cent less mass by the present day. One in three SIDM galaxies are entirely disrupted, compared to one in five CDM galaxies. However, the excess stripping will be harder to observe than suggested by previous DM-only simulations because the most stripped galaxies form cores and also lose stars: the most discriminating objects become unobservable. The best test will be to measure the stellar-to-halo mass relation (SHMR) for galaxies with stellar mass $10^{10-11}\,\mathrm{M}_{\odot}$. This is 8 times higher in a cluster than in the field for a CDM universe, but 13 times higher for an SIDM universe. Given intrinsic scatter in the SHMR, these models could be distinguished with noise-free galaxy-galaxy strong lensing of ${\sim}32$ cluster galaxies.