Constraining the cross-section of dark matter with giant radial arcs in galaxy clusters

TL;DR

This study compares the effects of self-interacting dark matter versus standard cold dark matter on the formation and properties of giant radial arcs in galaxy clusters, using simulations and ray-tracing.

Contribution

It introduces a novel analysis of radial arc statistics and morphology to distinguish between dark matter models in galaxy clusters.

Findings

Self-interacting dark matter produces fewer radial arcs.

Radial arcs in SIDM are more magnified.

Distinct arc morphologies can differentiate dark matter models.

Abstract

We compare the statistics and morphology of giant arcs in galaxy clusters using N-body and non-radiative SPH simulations within the standard cold dark matter model and simulations where dark matter has a non-negligible probability of interaction (parametrized by its cross-section), i.e self-interacting dark matter (SIDM). We use a ray-tracing technique to produce a statistically large number of arcs around six simulated galaxy clusters at different redshifts. Since dark matter is more likely to interact in colliding clusters than in relaxed clusters, and this probability of interaction is largest in denser regions, we focus our analysis on radial arcs (which trace the lensing potential in the central region better than tangential arcs) in galaxy clusters which underwent (or are undergoing) a major merger. We find that self-interacting dark matter produces fewer radial arcs than standard cold dark matter but they are on average more magnified. We also appreciate differences in the arc morphology that could be used to statistically favor one model versus the other.