Self-interacting Dark Matter: New Constraints from Galaxy Groups and Clusters

by Laura Sagunski

Longstanding anomalies in astrophysical observations on small scales suggest that dark matter might not be collisionless, as is commonly assumed, but could have sizable self-interactions. For the first time, we have probed the hypothesis of self-interacting dark matter (SIDM) at intermediate scales between galaxies and galaxy clusters. To model the SIDM halo density profiles, we have employed an observation-driven approach, the so-called Jeans model. So far, the limit on the self-interaction cross section from the Bullet Cluster is often cited as the strongest constraint on dark matter self-interactions. We show, however, that the halo density proles of relaxed systems like groups and clusters lead to much stronger bounds on the self-interaction cross section.