Influence of AGN jets on the magnetized ICM

TL;DR

This study uses high-resolution magneto-hydrodynamical simulations to show that AGN jets induce turbulence that amplifies magnetic fields in galaxy cluster cores, aligning with observed microGauss levels and preventing cooling flows.

Contribution

First simulation demonstrating how AGN jets sustain and amplify magnetic fields in galaxy cluster cores over Gyr timescales.

Findings

AGN jets induce turbulence that amplifies magnetic fields.

Magnetic field amplification exceeds pure compression effects.

AGN feedback prevents cooling flows and maintains observed magnetic field levels.

Abstract

Galaxy clusters are the largest structures for which there is observational evidence of a magnetised medium. Central cores seem to host strong magnetic fields ranging from a few 0.1 microG up to several 10 microG in cooling flow clusters. Numerous clusters harbor central powerful AGN which are thought to prevent cooling flows in some clusters. The influence of such feedback on the magnetic field remains unclear: does the AGN-induced turbulence compensate the loss of magnetic amplification within a cool core? And how is this turbulence sustained over several Gyr? Using high resolution magneto-hydrodynamical simulations of the self-regulation of a radiative cooling cluster, we study for the first time the evolution of the magnetic field within the central core in the presence of a powerful AGN jet. It appears that the jet-induced turbulence strongly amplifies the magnetic amplitude in the core beyond the degree to which it would be amplified by pure compression in the gravitational field of the cluster. The AGN produces a non-cooling core and increases the magnetic field amplitude in good agreement with microG field observations.