The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colours of galaxies

Abstract

We simulate the growth of galaxies and their central supermassive black holes by implementing a suite of semi‐analytic models on the output of the Millennium Run, a very large simulation of the concordance Λ cold dark matter cosmogony. Our procedures follow the detailed assembly history of each object and are able to track the evolution of all galaxies more massive than the Small Magellanic Cloud throughout a volume comparable to that of large modern redshift surveys. In this first paper we supplement previous treatments of the growth and activity of central black holes with a new model for ‘radio’ feedback from those active galactic nuclei that lie at the centre of a quasi‐static X‐ray‐emitting atmosphere in a galaxy group or cluster. We show that for energetically and observationally plausible parameters such a model can simultaneously explain: (i) the low observed mass drop‐out rate in cooling flows; (ii) the exponential cut‐off at the bright end of the galaxy luminosity function; and (iii) the fact that the most massive galaxies tend to be bulge‐dominated systems in clusters and to contain systematically older stars than lower mass galaxies. This success occurs because static hot atmospheres form only in the most massive structures, and radio feedback (in contrast, for example, to supernova or starburst feedback) can suppress further cooling and star formation without itself requiring star formation. We discuss possible physical models that might explain the accretion rate scalings required for our phenomenological ‘radio mode’ model to be successful.

The Co-Evolution of Galaxies and Black Holes: Current Status and Future Prospects

“…Models imply that the relative importance of the cold mode will increase at high redshifts and dominate in both the low and high mass galaxies (e.g., Keres et al 2005;Croton et al 2006). In such models, cold accretion can occur episodically, and many models link the formation of black holes to major merger events (e.g., Hopkins et al 2008;Di Matteo et al 2008).…”

“…A great deal of theoretical and observational effort is now being expended on understanding why this simple expectation does not appear to be borne out by observations. Matter accreting onto central supermassive black holes can, in principle, provide a vast source of energy, and jets or outflows can provide mechanisms for transporting the energy to large enough radii to regulate cooling and star formation in the massive galaxies where such black holes live (e.g., Churazov et al 2001;Croton et al 2006;Bower et al 2006;Hopkins et al 2008;Di Matteo et al 2008).…”

Characterizing the chemically enriched circumgalactic medium of ∼38 000 luminous red galaxies in SDSS DR12

“…While the observed low SFR and a predominantly old stellar population rules out a strong influence of young starburst driven winds on the halo gas of LRGs, the influence of AGN feedback can be dominant (e.g., McNamara & Nulsen 2007. In particular, radio-mode feedback has been invoked in galaxy formation models to suppress star formation in massive halos (e.g., Croton et al 2006). In addition, a cross-comparison between SDSS LRGs and FIRST radio sources has identified ≈ 3% of the LRGs hosting radio-loud AGN (e.g., Sadler et al 2007), and efforts in search of fainter radio emission in the remaining LRGs based on median stacks of FIRST images have continued to uncover radio signals at a level of a few × 10 µJy (e.g., Hodge et al 2008Hodge et al , 2009.…”

Dusty star-forming galaxies at high redshift

“…the new publicly available code, Galacticus Benson, 2012). Because of this, SAMs are readily used for isolating the effects of an individual astrophysical process (see Croton et al, 2006, for an example of this.). One promising way forward with SAMs is the construction of large grids of models that aim to constrain galaxy formation parameter spaces via comparison to observations through Markov Chain Monte Carlo models (e.g.…”