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

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 σ T /m at the ∼ 1 cm 2 g −1 level at v ∼ 2000 km s −1 .

Snowmass2021 Cosmic Frontier White Paper: Dark Matter Physics from Halo Measurements

“…In these systems, the interaction cross section at galactic velocities will be responsible for core formation or even the onset of gravothermal collapse [167], while the DM cross section at the higher cluster velocities would impact the ram-pressure stripping (evaporation) that subhalos experience as they move within the cluster halo. Thus, detailed observations of cluster substructure using both weak and strong gravitational lensing [336] could probe the DM cross section over a broad range of velocities [172]. Already, Ref.…”

Early-Universe Model Building

“…Evidence for self-interactions point toward a new dark mediator particle that is much lighter than the weak scale [23,[1197][1198][1199][1200]. In addition, the velocity dependence of the cross section could be tested with observations of galactic substructures [1201][1202][1203][1204]. Thus galactic halos act like particle colliders in probing the particle physics nature of DM.…”

Snowmass2021 Cosmic Frontier White Paper: Cosmological Simulations for Dark Matter Physics

“…dark photon mediator models) [43], many SIDM simulations only model the effects of self-interactions on the late-time evolution of DM. SIDM is typically assumed to interact elastically, with a velocity-independent cross section, though several simulations with inelastic and/or velocity-dependent interactions have been performed [103][104][105][106][107][108][109][110][111]. Self-interactions are simulated using modified N-body algorithms in which…”