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.