22-29 July 2015
Europe/Vienna timezone

Dark Matter Self-Interactions via Collisionless Shocks in Cluster Mergers

Jul 23, 2015, 3:30 PM


talk Astroparticle Physics, Cosmology, Gravitation Astroparticle Physics, Cosmology, Gravitation


Christian Spethmann


While dark matter self-interactions may solve several problems with structure formation, so far only the effects of two-body scatterings of dark matter particles have been considered. We show that, if a subdominant component of dark matter is charged under an unbroken U(1) gauge group, collective dark plasma effects need to be taken into account to understand its dynamics. Plasma instabilities can lead to collisionless dark matter shocks in galaxy cluster mergers which might have been already observed in the Abell 3827 and 520 clusters. As a concrete model we propose a thermally produced dark pair plasma of vectorlike fermions. In this scenario the interacting dark matter component is expected to be separated from the stars and the non-interacting dark matter halos in cluster collisions. In addition, the missing satellite problem is softened, while constraints from all other astrophysical and cosmological observations are avoided.

Primary author


Hardi Veermae (Nat. Inst. of Chem.Phys. & Biophys. (EE)) Martti Raidal (Nat. Inst. of Chem.Phys. & Biophys. (EE)) Matti Heikinheimo (York University, Toronto and Lapth, Annecy)

Presentation materials