The Role of Turbulence in AGN Self-Regulation in Galaxy Clusters

TL;DR

This paper presents hydrodynamical simulations demonstrating how turbulence driven by Rayleigh-Taylor instabilities enables active galactic nuclei to self-regulate heating and cooling in galaxy cluster cores over billions of years.

Contribution

It introduces a subgrid model for RT-driven turbulence, allowing realistic simulations of AGN feedback and self-regulation in galaxy clusters.

Findings

Clusters self-regulate for several Gyrs.

Heating and cooling balance through recurrent outbreaks.

Recurrence time of outbreaks is about 80 Myrs.

Abstract

Cool cores of galaxy clusters are thought to be heated by low-power active galactic nuclei (AGN), whose accretion is regulated by feedback. However, the interaction between the hot gas ejected by the AGN and the ambient intracluster medium is extremely difficult to simulate, as it involves a wide range of spatial scales and gas that is Rayleigh-Taylor (RT) unstable. Here we use a subgrid model for RT-driven turbulence to overcome these problems and present the first observationally-consistent hydrodynamical simulations of AGN self-regulation in galaxy clusters. For a wide range of parameter choices the cluster in our three-dimensional simulations regulates itself for at least several Gyrs years. Heating balances cooling through a string of outbreaks with a typical recurrence time of approximately 80 Myrs, a timescale that depends only on the global cluster properties.