The Interplay of Kinetic and Radiative Feedback in Galaxy Clusters

TL;DR

This study uses advanced simulations to investigate how kinetic and radiative feedback from supermassive black holes influence galaxy cluster cores, revealing the importance of both feedback modes in preventing cooling flows and correlating with cold gas structures.

Contribution

The paper introduces a comprehensive simulation approach combining kinetic and radiative feedback modes, demonstrating their joint impact on galaxy cluster core dynamics and SMBH state transitions.

Findings

Kinetic feedback is essential at all accretion rates to prevent cooling catastrophe.

Kinetic feedback contributes over 10% of total AGN feedback power.

A positive correlation exists between AGN feedback power and cold gas filament mass.

Abstract

Recent observations provide evidence that some cool-core clusters (CCCs) host quasars in their brightest cluster galaxies (BCGs). Motivated by these findings we use 3D radiation-hydrodynamic simulations with the code Enzo to explore the joint role of the kinetic and radiative feedback from supermassive black holes (SMBHs) in BCGs. We implement kinetic feedback as sub-relativistic plasma outflows and model radiative feedback using the ray-tracing radiative transfer or thermal energy injection. In our simulations the central SMBH transitions between the radiatively efficient and radiatively inefficient states on timescales of a few Gyr, as a function of its accretion rate. The timescale for this transition depends primarily on the fraction of power allocated to each feedback mode, and to a lesser degree on the overall feedback luminosity of the active galactic nucleus (AGN). Specifically, we find that (a) kinetic feedback must be present at both low and high accretion rates in order to prevent the cooling catastrophe, and (b) its contribution likely accounts for > 10% of the total AGN feedback power, since below this threshold simulated BCGs tend to host radio-loud quasars most of the time, in apparent contrast with observations. We also find a positive correlation between the AGN feedback power and the mass of the cold gas filaments in the cluster core, indicating that observations of H$\alpha$ filaments can be used as a measure of AGN feedback.