The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe

Abstract

We summarize what large surveys of the contemporary (low-redshift) universe have taught us about the physics and phenomenology of the processes that link the formation and evolution of galaxies and their central supermassive black holes. The surveys are powerful because their large size and high data quality enable the careful control of systematics needed to untangle the complex inter-relationships in a robust way. We emphasize the particular importance of high-quality optical spectra from the Sloan Digital Sky Survey. We present a picture in the contemporary universe in which the population of Active Galactic Nuclei (AGN) can be divided into two distinct populations. The Radiative-Mode AGN are associated with black holes that produce radiant energy powered by accretion at rates in excess of ∼1% the Eddington Limit. This population today is primarily associated with less massive black holes growing in high-density pseudo-bulges at a rate sufficient to produce the total mass budget in these black holes in about 10 Gyr. The circumnuclear environment contains high density cold gas and associated on-going star-formation. Major mergers are not the primary mechanism for transporting this gas inward; secular processes appear dominant. The association between black hole growth and star-formation means that stellar feedback will be generic in these objects. Strong AGN feedback in the form of global outflows is seen only in the most powerful AGN. In the Jet-Mode AGN the bulk of energy extracted from the accretion process takes the form of collimated outflows (jets). This population is associated with the more massive black holes in the more massive (classical) bulges and elliptical galaxies. Neither the accretion onto these black holes nor star-formation in their host bulge is significant today. These AGN are probably fueled by the accretion of slowly cooling hot gas that is limited by the feedback/heating provided by AGN radio sources. Surveys of the high-redshift universe are painting a very similar picture for the characteristic population of AGN that are responsible for the bulk of the mass in relic black holes in today's fossil record: they live in normal galaxies with the (high) star-formation rates characteristic of those epochs. We speculate that a mode in which black holes are formed in major mergers and generate galaxy-scale winds may be responsible for the minority population lying above the knee in the AGN luminosity function. Noting that the volume-averaged ratio of star formation to black hole growth has remained broadly similar over the past 10 Gyrs, we argue that the processes that linked the cosmic evolution of galaxies and supermassive black holes are still at play today. All galaxies AGN: L bol /L Edd > 0.01 AGN: L bol /L Edd < 0.01 G ro w th Q ue nc hi ng Star-forming main sequence Red Sequence Fig. 2.-The distribution of galaxies in the SDSS main galaxy sample on the plane of stellar mass vs.specific star formation rate (sSFR = SFR/M * ). The greyscale indicates the volume-weighted distribution of all...

The jet feedback mechanism (JFM) in stars, galaxies and clusters

“…There is a large body of literature on feedback processes during the epoch of galaxy formation, including feedback from stars, mainly through supernovae, and from AGN, by radiation and/or jets/outflows (e.g., Cattaneo et al 2009;Alexander & Hickox 2012;Fabian 2012;Kormendy & Ho 2013;Heckman & Best 2014;King & Pounds 2015; Tadhunter 2016 for reviews, and, e.g., Wagner et al 2016;Bongiorno et al 2016;Weinberger et al 2016 for recent papers on the AGN-JFM). In this section I review only the AGN-JFM, and concentrate only on processes that are related to other objects that are reviewed here, in particular to cooling flows in clusters of galaxies.…”

Observational evidence that positive and negative AGN feedback depends on galaxy mass and jet power

“…Indeed, a consistent picture emerges whereby the availability of a cold gas supply regulates both the radiative-mode AGN and star formation activity (e.g. Hardcastle et al 2007;Heckman & Best 2014).…”

Constraints on Feedback in the Local Universe: The Relation Between Star Formation and Agn Activity in Early-Type Galaxies

“…The supply of cold gas to fuel star formation and AGN activity can include galaxy mergers/interactions, the cooling of gas in the ISM or surrounding hot halo, and the mass loss from stars (e.g., Heckman & Best 2014). The relation between radio power and SFR can provide some insight into the source of the fueling (Figure 10).…”