Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies

Abstract

A fundamental gap in the current understanding of galaxies concerns the thermodynamical evolution of ordinary, baryonic matter. On the one hand, radiative emission drastically decreases the thermal energy content of the interstellar plasma (ISM), inducing a slow cooling flow towards the centre. On the other hand, the active galactic nucleus (AGN) struggles to prevent the runaway cooling catastrophe, injecting huge amount of energy into the ISM. The present study intends to investigate thoroughly the role of mechanical AGN feedback in (isolated or massive) elliptical galaxies, extending and completing the mass range of tested cosmic environments. Our previously successful feedback models in galaxy clusters and groups demonstrated that AGN outflows, self‐regulated by cold gas accretion, are able to quench the cooling flow properly without destroying the cool core. Via three‐dimensional hydrodynamic simulations (flash 3.3), also including stellar evolution, we show that massive mechanical AGN outflows can indeed solve the cooling‐flow problem for the entire life of the galaxy, at the same time reproducing typical observational features and constraints such as buoyant underdense bubbles, elliptical shock cocoons, sonic ripples, dredge‐up of metals, subsonic turbulence and extended filamentary or nuclear cold gas. In order to avoid overheating and totally emptying the isolated galaxy, the frequent mechanical AGN feedback should be less powerful and efficient (ε∼ 10−4) compared with the heating required for more massive and bound ellipticals surrounded by the intragroup medium (ε∼ 10−3).

An overview of jet-mode AGN feedback and the prospects for studying its cosmic evolution with LOFAR

“…Similar results were found by Panagoulia et al (2014b), using volume limited sample (see also Dunn et al Fabian 2012). Furthermore, Panagoulia et al (2014b) noticed possible evidence of continuous "bubbling-mode" feedback for the lower mass systems, in agreement with gentle self-regulated feedback models (Gaspari et al 2011(Gaspari et al , 2012a. It is important to extend these studies to higher-redshift systems as well, and there is already plenty of Chandra data (e.g., on the SPT cluster sample; Bîrzan et al in preparation) and new spectral deprojection methods that have been developed to deal with the low numbers of counts available in observations of such systems (Sanders et al 2014).…”

The relation between gas density and velocity power spectra in galaxy clusters: High-resolution hydrodynamic simulations and the role of conduction

“…The AGN feedback balances cooling, preserving the cluster core in global quasi-thermal equilibrium (e.g. Gaspari et al 2012b). However, both processes just affect the inner region r < 0.1 R 500 (cf.…”

“…The amplitudes of the driven acceleration are evolved in Fourier space and then directly converted to physical space. Since observations (Schuecker et al 2004;Churazov et al 2008;de Plaa et al 2012;Sanders & Fabian 2013) and simulations (Norman & Bryan 1999;Lau et al 2009;Vazza et al 2009Vazza et al , 2011Gaspari et al 2012b;Schmidt et al 2014;Shi & Komatsu 2014) show that the ICM turbulent energies are ∼3-30 percent of the thermal energy, we test subsonic Mach numbers in the range of M ≡ σ v /c s ∼ 0.25-0.75, where σ v is the 3D 1 velocity dispersion (average sound speed of Coma is c s 1500 km s −1 ). The source of turbulence can be various, which includes cosmological flows/mergers, galaxy motions, and feedback processes.…”

“…Rebusco et al 2005), the deposition of energy imparted by the active galactic nucleus (AGN) outflows (e.g. Churazov et al 2004;Gaspari et al 2011bGaspari et al , 2012b, the evolution of filaments and bubbles (e.g. Scannapieco & Brüggen 2008), or the reacceleration of cosmic rays (e.g.…”

The diversity of growth histories of Milky Way-mass galaxies

“…This causes rapid growth of the black hole and high accretion disc luminosities (Kauffmann & Haehnelt, 2000;Di Matteo et al, 2005), as well as massive outflows of gas (Sturm et al, 2011;Cicone et al, 2014). After this phase, radio-mode feedback begins where gas from the hot halo is fed into the black hole inefficiently, producing a jet which heats the surrounding gaseous atmosphere (Page et al, 2012;Gaspari et al, 2012;Dubois et al, 2013;Man et al, 2014).…”