Radio relics in cosmological simulations

TL;DR

This paper uses high-resolution cosmological simulations to model the formation and properties of radio relics in galaxy clusters, providing predictions for their abundance in upcoming surveys.

Contribution

It introduces a detailed simulation framework for radio relic formation, analyzing shock properties and predicting relic counts for future observations.

Findings

Broad Mach number distribution in simulated shocks

Radio luminosity varies significantly with Mach number

Approximately a thousand relics expected in upcoming surveys

Abstract

Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers. Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by shock dissipation. Using high resolution cosmological simulations, identifying shock fronts and applying a parametric model for the radio emission allows us to simulate the formation of radio relics. We analyze a simulated shock front in detail. We find a rather broad Mach number distribution. The Mach number affects strongly the number density of relativistic electrons in the downstream area, hence, the radio luminosity varies significantly across the shock surface. The abundance of radio relics can be modeled with the help of the radio power probability distribution which aims at predicting radio relic number counts. Since the actual electron acceleration efficiency is not known, predictions for the number counts need to be normalized by the observed number of radio relics. For the characteristics of upcoming low frequency surveys we find that about thousand relics are awaiting discovery.