N-body + Magnetohydrodynamical Simulations of Merging Clusters of Galaxies: Characteristic Magnetic Field Structures Generated by Bulk Flow Motion

TL;DR

This study uses N-body and magnetohydrodynamical simulations to explore how galaxy cluster mergers generate characteristic magnetic field structures, revealing features like cold fronts and ordered fields observable via Faraday rotation.

Contribution

It demonstrates how merger-induced bulk flows produce distinct magnetic structures, including cold fronts and eddy-like fields, and discusses their observational signatures.

Findings

Magnetic field structures are shaped by bulk flows during mergers.

Cold fronts are associated with magnetic field configurations.

Faraday rotation maps can reveal these magnetic features.

Abstract

We present results from N-body + magnetohydrodynamical simulations of merging clusters of galaxies. We find that cluster mergers cause various characteristic magnetic field structures because of the strong bulk flows in the intracluster medium. The moving substructures result in cool regions surrounded by the magnetic field. These will be recognized as magnetized cold fronts in the observational point of view. A relatively ordered magnetic field structure is generated just behind the moving substructure. Eddy-like field configurations are also formed by Kelvin-Helmholtz instabilities. These features are similarly seen even in off-center mergers though the detailed structures change slightly. The above-mentioned characteristic magnetic field structures are partly recognized in Faraday rotation measure maps. The higher absolute values of the rotation measure are expected when observed along the collision axis, because of the elongated density distribution and relatively ordered field structure along the axis. The rotation measure maps on the cosmic microwave background radiation, which covers clusters entirely, could be useful probes of not only the magnetic field structures but also the internal dynamics of the intracluster medium.