MHD Simulations of AGN Jets in a Dynamic Galaxy Cluster Medium

TL;DR

This study uses 3D MHD simulations to examine how active galactic nucleus jets interact with the dynamic, weather-like motions of the intra-cluster medium in a relaxed galaxy cluster, revealing complex jet morphologies and cavity formations.

Contribution

It provides new insights into the impact of ICM motions on AGN jet morphology and cavity formation using realistic cosmological cluster simulations.

Findings

ICM motions significantly distort AGN jets and lobes.

Simulated jets produce complex cavities and bent structures similar to observed radio sources.

Jet cycling creates features akin to double-double radio galaxies.

Abstract

We present a pair of 3-d magnetohydrodynamical simulations of intermittent jets from a central active galactic nucleus (AGN) in a galaxy cluster extracted from a high resolution cosmological simulation. The selected cluster was chosen as an apparently relatively relaxed system, not having undergone a major merger in almost 7 Gyr. Despite this characterization and history, the intra-cluster medium (ICM) contains quite active "weather". We explore the effects of this ICM weather on the morphological evolution of the AGN jets and lobes. The orientation of the jets is different in the two simulations so that they probe different aspects of the ICM structure and dynamics. We find that even for this cluster that can be characterized as relaxed by an observational standard, the large-scale, bulk ICM motions can significantly distort the jets and lobes. Synthetic X-ray observations of the simulations show that the jets produce complex cavity systems, while synthetic radio observations reveal bending of the jets and lobes similar to wide-angle tail (WAT) radio sources. The jets are cycled on and off with a 26 Myr period using a 50% duty cycle. This leads to morphological features similar to those in "double-double" radio galaxies. While the jet and ICM magnetic fields are generally too weak in the simulations to play a major role in the dynamics, Maxwell stresses can still become locally significant.