Relics as probes of galaxy cluster mergers

TL;DR

This paper uses hydrodynamical simulations of galaxy cluster mergers to understand how radio relics form and to constrain merger parameters like mass ratios and impact angles.

Contribution

It introduces a method to constrain merger scenarios by analyzing the location, size, and width of radio relics in galaxy clusters.

Findings

Radio relic properties can constrain merger parameters

Simulations match observed relic features in CIZA J2242.8+5301

Merger scenarios can be inferred from relic morphology

Abstract

Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shocks within the intracluster medium (ICM). It is proposed that within the shocks particles can be accelerated to extreme energies. In the presence of a magnetic field these particles should then form large regions emitting synchrotron radiation, creating so-called radio relics. An example of a cluster with relics is CIZA J2242.8+5301. Here we present hydrodynamical simulations of idealized binary cluster collisions with the aim of constraining the merger scenario for this cluster. We conclude that by using the location, size and width of double radio relics we can set constraints on the mass ratios, impact parameters, timescales, and viewing geometries of binary cluster merger events.