The non-gravitational interactions of dark matter in colliding galaxy clusters

TL;DR

This study analyzes 72 galaxy cluster collisions to constrain dark matter's non-gravitational interactions, finding strong evidence for dark matter presence and setting stringent limits on its self-interaction cross-section.

Contribution

It provides the largest statistical analysis of dark matter interactions in colliding clusters, tightening constraints on self-interaction cross-section and testing extensions to the standard model.

Findings

Dark matter detected at 7.6σ significance.

Dark mass position closely aligned with stars within 5.8±8.2 kpc.

Self-interaction cross-section constrained to <0.47 cm²/g at 95% CL.

Abstract

Collisions between galaxy clusters provide a test of the non-gravitational forces acting on dark matter. Dark matter's lack of deceleration in the `bullet cluster collision' constrained its self-interaction cross-section \sigma_DM/m < 1.25cm2/g (68% confidence limit) for long-ranged forces. Using the Chandra and Hubble Space Telescopes we have now observed 72 collisions, including both `major' and `minor' mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6\sigma significance. The position of the dark mass has remained closely aligned within 5.8+/-8.2 kpc of associated stars: implying a self-interaction cross-section \sigma_DM/m < 0.47 cm2/g (95% CL) and disfavoring some proposed extensions to the standard model.