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The most luminous quasars do not live in the most massive dark matter haloes at any redshift

Fanidakis, N.; Macciò, A.V.; Baugh, C.M.; Lacey, C.G.; Frenk, C.S.

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N. Fanidakis

A.V. Macciò

C.S. Frenk


Quasars (QSOs) represent the brightest active galactic nuclei (AGN) in the Universe and are thought to indicate the location of prodigiously growing black holes (BHs), with luminosities as high as 1048 erg s−1. It is often expected though that such an extremely energetic process takes place in the most massive bound structures in the dark matter (DM) distribution. We show that in contrast to this expectation, in a galaxy formation model which includes AGN feedback, QSOs are predicted to live in DM haloes with typical masses of a few times 1012 M⊙. Such an environment is considered to be average in the low-redshift universe (z ≲ 2–3) and almost comparable to a Milky Way halo. This fundamental prediction arises from the fact that QSO activity (i.e. BH accretion with luminosity greater than 1046 erg s−1) is inhibited in more massive DM haloes, where AGN feedback operates. The galactic hosts of QSOs in our simulations have typical stellar masses of 1010–1011 M⊙, and represent remnants of massive disc galaxies that have undergone a disc instability or galaxy merger. Interestingly, we find no dependence of QSO activity on environment; thus, the typical QSO halo mass remains constant over two orders of magnitude in luminosity. We further show that the z ∼ 6 QSOs do not inhabit the largest DM haloes at that time as these environments are already subject to feedback. Their descendants at z = 0 span a wide range of morphologies and galaxy masses, and their BHs typically grow only by a modest factor between z ∼ 6 and the present day. We predict that there should be an enhancement in the abundance of galaxies around QSOs at z ∼ 5. However, these enhancements are considerably weaker compared to the overdensities expected at the extreme peaks of the DM distribution. Given that high-z QSO descendants are typically found in rich clusters (∼1014 M⊙) and very seldom in the most massive haloes, we conclude that it is very unlikely that QSOs observed at z ≳ 5 trace the progenitors of today's superclusters.


Fanidakis, N., Macciò, A., Baugh, C., Lacey, C., & Frenk, C. (2013). The most luminous quasars do not live in the most massive dark matter haloes at any redshift. Monthly Notices of the Royal Astronomical Society, 436(1), 315-326.

Journal Article Type Article
Publication Date Nov 21, 2013
Deposit Date May 16, 2014
Publicly Available Date Jul 3, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 436
Issue 1
Pages 315-326
Keywords Galaxies: haloes, Cosmology: theory, Dark matter, Large-scale structure of Universe.


Published Journal Article (3.1 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.

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