Simulations of galaxy cluster collisions with a dark plasma component^⋆

¹ National Institute of Chemical Physics and Biophysics, Rävala 10, 10143 Tallinn, Estonia
e-mail: christian.spethmann@kbfi.ee
² Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia
³ Tartu Observatory, Observatooriumi 1, Tõravere, 61602 Tartumaa, Estonia
⁴ Helsinki Institute of Physics, PO Box 64, University of Helsinki, 00014 Helsinki, Finland

Received: 2 June 2017
Accepted: 21 September 2017

Abstract

Context. Dark plasma is an intriguing form of self-interacting dark matter with an effective fluid-like behavior, which is well motivated by various theoretical particle physics models.

Aims. We aim to find an explanation for an isolated mass clump in the Abell 520 system, which cannot be explained by traditional models of dark matter, but has been detected in weak lensing observations.

Methods. We performed N-body smoothed particle hydrodynamics simulations of galaxy cluster collisions with a two component model of dark matter, which is assumed to consist of a predominant non-interacting dark matter component and a 10–40% mass fraction of dark plasma.

Results. The mass of a possible dark clump was calculated for each simulation in a parameter scan over the underlying model parameters. In two higher resolution simulations shock-waves and Mach cones were observed to form in the dark plasma halos.

Conclusions. By choosing suitable simulation parameters, the observed distributions of dark matter in both the Bullet cluster (1E 0657-558) and Abell 520 (MS 0451.5+0250) can be qualitatively reproduced.