A Stringent Upper Limit on Dark Matter Self-Interaction Cross Section from Cluster Strong Lensing

TL;DR

This study uses strong gravitational lensing in galaxy clusters to place a stringent upper limit on the self-interaction cross section of dark matter particles, supporting the collisionless dark matter model.

Contribution

It introduces a novel method combining strong lensing data and simulations to tightly constrain dark matter self-interactions in galaxy clusters.

Findings

Inferred dark matter self-interaction cross section is less than 0.13 cm²/g at 95% confidence.

Method validated with mock data from Illustris-TNG simulations showing no self-interactions.

Results support the collisionless dark matter paradigm with very low self-interaction cross section.

Abstract

We analyze strongly lensed images in 8 galaxy clusters to measure their dark matter density profiles in the radial region between 10 kpc and 150 kpc, and use this to constrain the self-interaction cross section of dark matter (DM) particles. We infer the mass profiles of the central DM halos, bright central galaxies, key member galaxies, and DM subhalos for the member galaxies for all 8 clusters using the Qlens code. The inferred DM halo surface densities are fit to a self-interacting dark matter (SIDM) model, which allows us to constrain the self-interaction cross section over mass $\sigma$/m. When our full method is applied to mock data generated from two clusters in the Illustris-TNG simulation, we find results consistent with no dark matter self-interactions as expected. For the eight observed clusters with average relative velocities of $1458_{-81}^{+80}$ km/s, we infer $\sigma$/m = $0.082_{-0.021}^{+0.027}$ cm$^2$/g and $\sigma$/m < 0.13 cm$^2$/g at the 95% confidence level.