Magnetorotational instability in cool cores of galaxy clusters

TL;DR

This paper investigates how the magnetorotational instability (MRI) influences the stability and evolution of cool cores in galaxy clusters, highlighting its potential dominance in certain regions and the importance of measuring ICM rotation.

Contribution

It demonstrates that MRI can be a dominant instability in rotating cool-core galaxy clusters, suggesting new dynamics and evolution pathways for these structures.

Findings

MRI can dominate over other instabilities in parts of cool-core clusters.

Rotation significantly alters the stability properties of the intracluster medium.

Future X-ray missions could measure ICM rotation to test these predictions.

Abstract

Clusters of galaxies are embedded in halos of optically thin, gravitationally stratified, weakly magnetized plasma at the system's virial temperature. Due to radiative cooling and anisotropic heat conduction, such intracluster medium (ICM) is subject to local instabilities, which are combinations of the thermal, magnetothermal and heat-flux-driven buoyancy instabilities. If the ICM rotates significantly, its stability properties are substantially modified and, in particular, also the magnetorotational instability (MRI) can play an important role. We study simple models of rotating cool-core clusters and we demonstrate that the MRI can be the dominant instability over significant portions of the clusters, with possible implications for the dynamics and evolution of the cool cores. Our results give further motivation for measuring the rotation of the ICM with future X-ray missions such as ASTRO-H and ATHENA.