Evolution and structure of magnetic fields in simulated galaxy clusters

TL;DR

This study uses cosmological magneto-hydrodynamic simulations to analyze the evolution and structure of magnetic fields in galaxy clusters, revealing their correlation with density profiles, power spectrum characteristics, and growth patterns across different cosmologies.

Contribution

It provides detailed simulation-based insights into magnetic field evolution in galaxy clusters, including their correlation with density, power spectrum, and effects of mergers, across different cosmological models.

Findings

Magnetic field strength profiles follow cluster density profiles outside the core.

Magnetic fields have a correlation length of about 50 kpc and reverse on scales of 100 kpc.

Simulated Faraday rotation matches observations with nG seed fields.

Abstract

We use cosmological magneto-hydrodynamic simulations to study the evolution of magnetic fields in galaxy clusters in two different cosmological models, a standard-CDM and a $\Lambda$-CDM model. We show that the magnetic field strength profiles closely follow the cluster density profiles outside a core region of radius $\sim200\kpc$. The magnetic field has a correlation length of order $50\kpc$ and reverses on scales of $\sim100\kpc$ along typical lines-of-sight. The power spectrum of the magnetic field can well be approximated by a steep power law with an exponent of $\sim-2.7$. The mean magnetic field in the cluster cores grows roughly exponentially with decreasing redshift, $B\sim10^{-2.5z} \muG$. Merger events have a pronounced effect on magnetic field evolution, which is strongly reflected in measurable quantities like the Faraday rotation. The field evolution in the two different cosmologies proceeds virtually identically. All our cluster models very well reproduce observed Faraday rotation measurements when starting with nG seed fields.