Speaker
Description
Galaxy–mass offsets in cluster collisions were once considered a promising signal for constraining the self-interaction cross-section of dark matter. However, previous studies based on these offsets have been hindered by large measurement uncertainties and poorly constrained merger phases and geometries. In this work, we overcome these challenges and present a robust constraint on the dark matter self-interaction cross-section using a new and powerful method applied to ten cluster collisions hosting double radio relics. By utilizing the relic–relic separation relative to the halo–halo distance as an indicator of dark matter properties, we derive a 68% upper limit of ~0.30 cm² g⁻¹ on the self-interaction cross-section. This represents the first robust result obtained from large halo colliders, incorporating full marginalization over mass uncertainty, viewing angle, collision speed, merger phase, impact parameter, and gas slope.
