Collisionless shocks in self-interacting dark matter

TL;DR

This paper investigates how collisionless shocks form in self-interacting dark matter models, especially those involving dark electromagnetism, and discusses their impact on dark matter distribution in galaxy cluster mergers.

Contribution

It provides a detailed analysis of shock formation scales in charged dark matter models and explores their implications for cosmological simulations.

Findings

Shock formation scales are critical for understanding dark matter distribution.

Charged dark matter can produce collisionless shocks similar to baryonic plasma.

Implications for galaxy cluster observations and dark matter modeling.

Abstract

Self-interacting dark matter has been proposed as a solution to small scale problems in cosmological structure formation, and hints of dark matter self scattering have been observed in mergers of galaxy clusters. One of the simplest models for self-interacting dark matter is a particle that is charged under dark electromagnetism, a new gauge interaction analogous to the usual electromagnetic force, but operating on the dark matter particle instead of the visible particles. In this case, the collisional behaviour of dark matter is primarily due to the formation of collisionless shocks, that should affect the distribution of DM in merging galaxy clusters. We evaluate the time and length scales of shock formation in cluster mergers, and discuss the implications for modelling charged dark matter in cosmological simulations.