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Do we expect most AGN to live in discs?

Hopkins, Philip F. and Kocevski, Dale D. and Bundy, Kevin (2014) Do we expect most AGN to live in discs? Monthly Notices of the Royal Astronomical Society, 445 (1). pp. 823-834. ISSN 0035-8711. doi:10.1093/mnras/stu1736.

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Recent observations have indicated that a large fraction of the low- to intermediate-luminosity AGN population lives in disc-dominated hosts, while the more luminous quasars live in bulge-dominated hosts (that may or may not be major merger remnants), in conflict with some previous model predictions. We therefore build and compare a semi-empirical model for AGN fuelling which accounts for both merger and non-merger ‘triggering’. In particular, we show that the ‘stochastic accretion’ model – in which fuelling in disc galaxies is essentially a random process arising whenever dense gas clouds reach the nucleus – provides a good match to the present observations at low/intermediate luminosities. However, it falls short of the high-luminosity population. We combine this with models for major merger-induced AGN fueling, which lead to rarer but more luminous events, and predict the resulting abundance of disc-dominated and bulge-dominated AGN host galaxies as a function of luminosity and redshift. We compile and compare observational constraints from z ∼ 0 to 2. The models and observations generically show a transition from disc to bulge dominance in hosts near the Seyfert-quasar transition, at all redshifts. ‘Stochastic’ fuelling dominates AGN by number (dominant at low luminosity), and dominates black hole (BH) growth below the ‘knee’ in the present-day BH mass function ( ≲ 10^7  M_⊙). However, it accounts for just ∼10 per cent of BH mass growth at masses ≳ 10^8  M_⊙. In total, fuelling in discy hosts accounts for ∼30 per cent of the total AGN luminosity density/BH mass density. The combined model also accurately predicts the AGN luminosity function and clustering/bias as a function of luminosity and redshift; however, we argue that these are not sensitive probes of BH fuelling mechanisms.

Item Type:Article
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URLURL TypeDescription Paper
Hopkins, Philip F.0000-0003-3729-1684
Bundy, Kevin0000-0001-9742-3138
Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 August 22. Received 2014 August 21; in original form 2013 September 15. Support for PFH was provided by NASA through Einstein Postdoctoral Fellowship Award Number PF1-120083 issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060. KB was supported by the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan.
Funding AgencyGrant Number
NASA Einstein FellowshipPF1-120083
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Subject Keywords:galaxies: active; galaxies: evolution; galaxies: formation; cosmology: theory
Issue or Number:1
Record Number:CaltechAUTHORS:20141201-101549262
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Official Citation:Hopkins, P. F., Kocevski, D. D., & Bundy, K. (2014). Do we expect most AGN to live in discs? Monthly Notices of the Royal Astronomical Society, 445(1), 823-834. doi: 10.1093/mnras/stu1736
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52212
Deposited By: Jason Perez
Deposited On:01 Dec 2014 21:25
Last Modified:10 Nov 2021 19:22

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