Evolution of shocks and turbulence in the formation of galaxy clusters embedded in Megaparsec-scale filaments

TL;DR

This paper uses cosmological simulations to study how shocks and turbulence develop during galaxy cluster formation within cosmic filaments, revealing long turbulence decay timescales and structures similar to observed radio relics.

Contribution

It provides new insights into the interaction of merger shocks with cosmic web filaments and the long-lived turbulence in merging galaxy clusters.

Findings

Peripheral structures similar to giant radio relics are produced.

Turbulence decay timescale is about 4 Gyr, longer than previously assumed.

Interaction with filaments influences shock and turbulence evolution.

Abstract

Massive structures like cluster of galaxies, embedded in cosmic filaments, release enormous amount of energy through their interactions. These events are associated with production of Mpc-scale shocks and injection of considerable amount of turbulence, affecting the non-thermal energy budget of the ICM. In order to study this thoroughly, we performed a set of cosmological simulations using the hydrodynamical code Enzo. We studied the formation of clusters undergoing major mergers, the propagation of merger shocks and their interaction with the filamentary cosmic web. This interaction is shown to produce peripheral structures remarkably similar to giant radio relics observed, for example, in Abell 3376 and Abell 3667. We find a relatively long timescale (about 4 Gyr) for turbulence decay in the centre of major merging clusters. This timescale is substantially longer than typically assumed in the turbulent re-acceleration models, invoked for explaining the statistics of observed radio halos.