Shock heating by FR I radio sources in galaxy clusters

TL;DR

This paper uses 3D simulations to study how AGN jets create weak shock fronts in galaxy clusters, dissipating a small but significant part of their energy and influencing cluster dynamics.

Contribution

It provides the first detailed analysis of shock dissipation from AGN jets in realistic cluster environments using high-resolution 3D simulations.

Findings

Weak shocks have Mach numbers of 1.1-1.2.

At least 2% of AGN mechanical energy is dissipated in shocks.

Multiple shock structures can form, affecting AGN duty cycle estimates.

Abstract

Feedback by active galactic nuclei (AGN) is frequently invoked to explain the cut-off of the galaxy luminosity function at the bright end and the absence of cooling flows in galaxy clusters. Meanwhile, there are recent observations of shock fronts around radio-loud AGN. Using realistic 3D simulations of jets in a galaxy cluster, we address the question what fraction of the energy of active galactic nuclei is dissipated in shocks. We find that weak shocks that encompass the AGN have Mach numbers of 1.1-1.2 and dissipate at least 2% of the mechanical luminosity of the AGN. In a realistic cluster medium, even a continuous jet can lead to multiple shock structures, which may lead to an overestimate of the AGN duty cycles inferred from the spatial distribution of waves.