AGN jet feedback on a moving mesh: lobe energetics and X-ray properties in a realistic cluster environment

Abstract

Jet feedback from active galactic nuclei (AGN) harboured by brightest cluster galaxies is expected to play a fundamental role in regulating cooling in the intracluster medium (ICM). While observations and theory suggest energy within jet lobes balances ICM radiative losses, the modus operandi of energy communication with the ICM remains unclear. We present simulations of very high-resolution AGN-driven jets launching in a live, cosmological galaxy cluster, within the moving mesh-code arepo. As the jet propagates through the ICM the majority of its energy, which is initially in the kinetic form, thermalises quickly through internal shocks and inflates lobes of very hot gas. The jets effectively heat the cluster core, with PdV work and weather-aided mixing being the main channels of energy transfer from the lobes to the ICM, while strong shocks and turbulence are sub-dominant. We additionally present detailed mock Xray maps at different stages of evolution, revealing clear cavities surrounded by X-ray bright rims, with lobes being detectable for up to ∼ 10 8 yrs even when magnetic draping is ineffective. We find bulk motions in the cluster can significantly affect lobe propagation, offsetting them from the jet direction and imparting bulk velocities that can dominate over the buoyantly-rising motion.

Blandford-Znajek jets in galaxy formation simulations: method and implementation

“…Zoom-in simulations of cosmological clusters somewhat address the resolution problems associated with full cosmological box simulations. Indeed, individual jet studies that follow the lobe inflation process in a live cosmological environment have been carried out (Bourne & Sijacki 2020;Bourne et al 2019;Dubois et al 2010;Morsony et al 2010;Heinz et al 2006).…”

“…Despite these problems, the modelling of jet feedback in galaxy and cosmological scale simulations is becoming more sophisticated, incorporating more accurate modelling of (computationally) complex physical processes such as magnetic fields and cosmic rays (Yang et al 2019;Ehlert et al 2018;Weinberger et al 2017b). Jet studies are also now finding that they are able to reproduce features seen in radio and X-ray observations with unprecedented accuracy (Bourne & Sijacki 2020;Bourne et al 2019). With these advances in mind it is timely to ensure that self-regulation of the jet feedback is fully investigated in these contexts.…”

Connecting turbulent velocities and magnetic fields in galaxy cluster simulations with active galactic nuclei jets

“…The details of the heating process are unknown. Possible mechanisms include mixing of hot bubble gas with the ICM (Yang & Reynolds 2016;Hillel & Soker 2017b, possibly facilitated by external cluster turbulence (Bourne et al 2019;Bourne & Sijacki 2020), the decay of turbulence (Zhuravleva et al 2014(Zhuravleva et al , 2018Fujita et al 2020;Mohapatra & Sharma 2019), the uplift of cold gas in the wake of bubbles (Guo et al 2018;Chen et al 2019), the dissipation of sound waves (Fabian et al E-mail: kehlert@aip.de 2017; Tang & Churazov 2017;Bambic & Reynolds 2019), the dissipation of weak shocks (Li et al 2017;Martizzi et al 2019) or the damping of cosmic ray (CR) induced Alfvén waves (Loewenstein et al 1991;Guo & Oh 2008;Enßlin et al 2011;Pfrommer 2013;Jacob & Pfrommer 2017a,b;Ruszkowski et al 2017). The structure of the velocity field in the ICM contains important information about the relevance of many of these processes: the amplitude and scale of the ICM turbulence can be used to infer a turbulent dissipation rate (Zhuravleva et al 2014), turbulent velocities combined with the cooling time set an effective range for turbulent transport (Fabian et al 2017) and the morphology of the magnetic and velocity field impacts the transport of CRs (Ehlert et al 2018).…”

Two striking head-tail galaxies in the galaxy cluster IIZW108: insights into transition to turbulence, magnetic fields and particle re-acceleration

“…The physics of this interaction regulates the amount of cooling and star formation via dissipation of mechanical heat by outflows, lobes, or sound waves from the AGN (e.g., Churazov et al 2001;Brüggen & Kaiser 2002;Ruszkowski & Begelman 2002;Ruszkowski et al 2004;Brüggen et al 2005;Gaspari et al 2012) or due to cosmic rays escaping from the jet lobes that resonantly drive Alfvén waves, which are damped and thereby heat the ambient cooling ICM (Guo & Oh 2008;Pfrommer 2013;Jacob & Pfrommer 2017a,b;Ruszkowski et al 2017;Ehlert et al 2018). Simulations of interactions of AGN jets with a realistic magnetized and/or turbulent ICM (Brüggen et al 2005;Heinz et al 2006;Sijacki et al 2008;O'Neill & Jones 2010;Mendygral et al 2011;Weinberger et al 2017;Bourne & Sijacki 2017;Bourne et al 2019;Ehlert et al 2021) enable to probe the characteristics of ICM turbulence, the filling of the AGN jet lobes through the Sunyaev-Zel'dovich effect (Pfrommer et al 2005;Ehlert et al 2019), and enable to indirectly infer the dynamical state of the local ICM through observations of the radio morphologies of HT galaxies (Pfrommer & Jones 2011;Jones et al 2017). In particular, simulations of NAT galaxies with passive cosmic ray electrons (O'Neill et al 2019a) that encounter the passage of (possibly oblique) shocks (O'Neill et al 2019b;Nolting et al 2019a,b) can be used to produce synthetic radio observations and to study turbulence and particle acceleration in the jet lobes.…”