Looking for dark matter trails in colliding galaxy clusters

TL;DR

This study investigates potential non-gravitational interactions of dark matter in colliding galaxy clusters by analyzing weak gravitational lensing data, aiming to detect signs of dark matter scattering.

Contribution

The paper introduces a novel method to detect dark matter self-interactions through asymmetries in mass profiles during galaxy cluster collisions, using weak lensing data.

Findings

Detected weak lensing signal of trailing gas at 4σ confidence

Found no evidence for scattered dark matter particles with a scattering fraction of 0.03±0.05

Estimated that reducing positional error to <2.5" could detect a 10% scattering fraction at 3σ

Abstract

If dark matter interacts, even weakly, via non-gravitational forces, simulations predict that it will be preferentially scattered towards the trailing edge of the halo during collisions between galaxy clusters. This will temporarily create a non-symmetric mass profile, with a trailing over-density along the direction of motion. To test this hypothesis, we fit (and subtract) symmetric halos to the weak gravitational data of 72 merging galaxy clusters observed with the Hubble Space Telescope. We convert the shear directly into excess {\kappa} and project in to a one dimensional profile. We generate numerical simulations and find that the one dimensional profile is well described with simple Gaussian approximations. We detect the weak lensing signal of trailing gas at a 4{\sigma} confidence, finding a mean gas fraction of Mgas/Mdm = 0.13 +/- 0.035. We find no evidence for scattered dark matter particles with a estimated scattering fraction of f = 0.03 +/- 0.05. Finally we find that if we can reduce the statistical error on the positional estimate of a single dark matter halo to <2.5", then we will be able to detect a scattering fraction of 10% at the 3{\sigma} level with current surveys. This poten- tially interesting new method can provide an important independent test for other complimentary studies of the self-interaction cross-section of dark matter.