An examination of magnetized outflows from active galactic nuclei in galaxy clusters

TL;DR

This study uses 3D MHD simulations to explore how active galactic nuclei influence magnetic field formation in galaxy clusters, comparing jet and bubble models and their effects on cluster properties.

Contribution

It evaluates different AGN feedback models in simulations to understand their impact on cluster magnetic fields and thermodynamics, highlighting the effectiveness of bubble models.

Findings

Bubble models best reproduce observed magnetic fields.

Jet models show reduced black hole accretion rates.

Model outcomes are sensitive to simulation parameters.

Abstract

We present 3D adaptive mesh refinement MHD simulations of an isolated galaxy cluster that include injection of kinetic, thermal, and magnetic energy via a central active galactic nucleus (AGN) in order to study and evaluate the role that AGN may play in producing the observed cluster-wide magnetic fields. Using the MHD solver in FLASH 3.3, we compare several sub-resolution approaches to the evolution of AGN, specifically focusing on large-scale jet and bubble models. We examine the effects of magnetized outflows on the accretion history of the black hole and cluster thermodynamic properties, discuss the ability of various models to magnetize the cluster medium, and assess the sensitivity of these models to their underlying subgrid parameters. We find that magnetized jet-based models suffer a severe reduction in accretion rate compared to hydrodynamic jets; however, bubble models remain largely unaffected. While both jets and sporadically-placed bubbles have difficulty reproducing the observed strength and topology of cluster magnetic fields, models based on centrally-located bubbles come closest to observations. Finally, whereas jet models are relatively insensitive to changes in their subgrid parameters, the accretion rate and average magnetic field produced by the bubbles vary by as much as an order of magnitude depending on the grid resolution and accretion strength.