The Signatures of Self-Interacting Dark Matter and Subhalo Disruption on Cluster Substructure

TL;DR

This study uses cosmological simulations to analyze how self-interacting dark matter affects galaxy cluster substructure, revealing differences in subhalo abundance and inner density profiles that could be distinguished through weak lensing observations.

Contribution

The paper presents the first detailed simulation-based analysis of SIDM effects on cluster subhalos, including the potential for observational constraints via weak lensing.

Findings

Subhalo abundance is suppressed in SIDM compared to CDM.

Inner density profiles of subhalos differ significantly between SIDM and CDM.

Future surveys can constrain SIDM cross-sections using weak lensing measurements.

Abstract

The abundance, distribution and inner structure of satellites of galaxy clusters can be sensitive probes of the properties of dark matter. We run 30 cosmological zoom-in simulations with self-interacting dark matter (SIDM), with a velocity-dependent cross-section, to study the properties of subhalos within cluster-mass hosts. We find that the abundance of subhalos that survive in the SIDM simulations are suppressed relative to their cold dark matter (CDM) counterparts. Once the population of disrupted subhalos -- which may host orphan galaxies -- are taken into account, satellite galaxy populations in CDM and SIDM models can be reconciled. However, even in this case, the inner structure of subhalos are significantly different in the two dark matter models. We study the feasibility of using the weak lensing signal from the subhalo density profiles to distinguish between the cold and self-interacting dark matter while accounting for the potential contribution of orphan galaxies. We find that the effects of self-interactions on the density profile of subhalos can appear degenerate with subhalo disruption in CDM, when orphans are accounted for. With current error bars from the Subaru Hyper Suprime-Cam Strategic Program, we find that subhalos in the outskirts of clusters (where disruption is less prevalent) can be used to constrain dark matter physics. In the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time will give precise measurements of the weak lensing profile and can be used to constrain $\sigma_T/m$ at the $\sim 1$ cm$^2$ g$^{-1}$ level at $v\sim 2000$ km s$^{-1}$.