The complex interplay of AGN jet-inflated bubbles and the intracluster medium

TL;DR

This study uses hydrodynamic simulations to explore how AGN jets inflate bubbles that interact with the intracluster medium, revealing energy transfer, filament formation, and feedback mechanisms that influence cluster thermodynamics.

Contribution

The paper presents detailed simulations showing the evolution of AGN-inflated bubbles and their impact on the ICM, highlighting the role of buoyancy and gas uplift in feedback processes.

Findings

Most jet energy is transferred to the ICM quickly after jets turn off.

Bubbles create low-entropy filaments similar to observations.

Uplift of gas alters the ICM thermodynamics, reducing central density and delaying cooling.

Abstract

We use SWIFT, a smoothed particle hydrodynamics code, to simulate the evolution of bubbles inflated by active galactic nuclei (AGN) jets, as well as their interactions with the ambient intracluster medium (ICM). These jets inflate lobes that turn into bubbles after the jets are turned off (at $t=50$ Myr). Almost all of the energy injected into the jets is transferred to the ICM very quickly after they are turned off, with roughly $70$ per cent of it in thermal form and the rest in kinetic. At late times ($t>500$ Myr) we find the following: 1) the bubbles draw out trailing filaments of low-entropy gas, similar to those recently observed, 2) the action of buoyancy and the uplift of the filaments dominates the energetics of both the bubbles and the ICM and 3) almost all of the originally injected energy is in the form of gravitational potential energy, with the bubbles containing $15$ per cent of it, and the rest contained in the ICM. These findings indicate that feedback proceeds mainly through the displacement of gas to larger radii. We find that the uplift of these filaments permanently changes the thermodynamic properties of the ICM by reducing the central density and increasing the central temperature (within $30$ kpc). We propose that jet feedback proceeds not only through the heating of the ICM (which can delay cooling), but also through the uplift-related reduction of the central gas density. The latter also delays cooling, on top of reducing the amount of gas available to cool.