Energetic Impact of Jet Inflated Cocoons in Relaxed Galaxy Clusters

TL;DR

This study uses hydrodynamic simulations to analyze how AGN jets inflate cocoons in galaxy clusters, affecting the energy distribution and entropy in the intracluster medium over time.

Contribution

It provides a parameter survey of jet-ICM interactions, linking morphological classes to energy injection and entropy increase in galaxy clusters.

Findings

Cocoon-bounded sources inject more entropy into the ICM core.

Energy thermalization efficiency is independent of source morphology.

A large fraction of jet energy increases the gravitational potential energy of the cluster.

Abstract

Jets from active galactic nuclei (AGN) in the cores of galaxy clusters have the potential to be a major contributor to the energy budget of the intracluster medium (ICM). To study the dependence of the interaction between the AGN jets and the ICM on the parameters of the jets themselves, we present a parameter survey of two-dimensional (axisymmetric) ideal hydrodynamic models of back-to-back jets injected into a cluster atmosphere (with varying Mach numbers and kinetic luminosities). We follow the passive evolution of the resulting structures for several times longer than the active lifetime of the jet. The simulations fall into roughly two classes, cocoon-bounded and non-cocoon bounded sources. We suggest a correspondence between these two classes and the Faranoff-Riley types. We find that the cocoon-bounded sources inject significantly more entropy into the core regions of the ICM atmosphere, even though the efficiency with which energy is thermalized is independent of the morphological class. In all cases, a large fraction (50--80%) of the energy injected by the jet ends up as gravitational potential energy due to the expansion of the atmosphere.