Journal Article

Do all QSOs have the same black hole mass?

T. Shanks, S. M. Croom, S. Fine, N. P. Ross and U. Sawangwit

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 1, pages 650-659
Published in print September 2011 | ISSN: 0035-8711
Published online August 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19076.x
Do all QSOs have the same black hole mass?

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Quasi-stellar objects (QSOs) from SDSS, 2QZ and 2SLAQ covering an order of magnitude in luminosity at fixed redshift exhibit similar amplitudes of clustering, with the brightest sample showing a clustering length only 11 ± 9 per cent higher than the faintest sample. In addition, QSO clustering evolution at z > 0.5 is well fitted by a model that assumes a fixed host halo mass. If halo and black hole (BH) masses are related, then this may imply that QSOs occur in a relatively narrow range of halo masses with a correspondingly narrow range of BH mass. Hubble Space Telescope and Gemini high-resolution imaging of QSOs covering a large range in luminosity also show a relatively narrow range in QSO host galaxy luminosity. We argue that the slow evolution of early-type galaxies out to z≈ 1–2 may also provide further support for a slow evolution of QSO host BH masses. The result would mean that if high-z QSOs radiate at Eddington rates then low-z type 1 Seyfert galaxy must radiate at ≈100 times less than Eddington. We discuss the consequences in terms of four empirical models where (i) QSOs radiate at a fixed fraction of LEdd, (ii) QSO luminosity ‘flickers’ over time, (iii) QSOs have a single BH mass and (iv) QSOs are long lived and evolve via pure luminosity evolution (PLE). We conclude that the LEdd model requires MBH and Mhalo to be decoupled to circumvent the clustering results. While the single BH mass and flickering models fit the z > 0.5 clustering results, they appear to be rejected by the MBHL relation found from reverberation mapping at z≈ 0. We find that the inclusion of z < 0.5 QSO clustering data improves the fit of a long-lived QSO model and suggest that the predictions of the PLE model for QSO BH masses agree reasonably with ultraviolet bump and reverberation estimates.

Keywords: quasars: general

Journal Article.  9019 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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