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The optical-UV emissivity of quasars: dependence on black hole mass and radio loudness

The optical-UV emissivity of quasars: dependence on black hole mass and radio loudness
The optical-UV emissivity of quasars: dependence on black hole mass and radio loudness
We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 ≤ z ≤ 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) α3000 continuum slopes (Lν ∝  να at 3000 Å) with increasing black hole mass, bluer α3000 with increasing luminosity at 3000 Å, and bluer α3000 with increasing spin of the black hole, when all other parameters are held fixed. We find no clear evidence for any of these predictions in the data. In particular, we find the following. (i) α3000 shows no significant dependence on black hole mass or luminosity. Dedicated Monte Carlo tests suggest that the substantial observational uncertainties in the black hole virial masses can effectively erase any intrinsic dependence of α3000 on black hole mass, in line with some previous studies. (ii) The mean slope α3000 of radio-loud sources, thought to be produced by rapidly spinning black holes, is comparable to, or even redder than, that of radio-quiet quasars. Indeed, although quasars appear to become more radio loud with decreasing luminosity, we still do not detect any significant dependence of α3000 on radio loudness. The predicted mean α3000 slopes tend to be bluer than in the data. Disk models with high inclinations and dust extinction tend to produce redder slopes closer to empirical estimates. Our mean α3000 values are close to the ones independently inferred at z < 0.5, suggesting weak evolution with redshift, at least for moderately luminous quasars.
1538-4357
1-6
Shankar, Francesco
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Calderone, Giorgio
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Knigge, Christian
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Matthews, James
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Buckland, Rachel
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Hryniewicz, Krzysztof
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Sivakoff, Gregory
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Dai, Xinyu
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Richardson, Kayleigh
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Riley, Jack
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Gray, James
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La Franca, Fabio
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Altamirano, Diego
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Croston, Judith
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Gandhi, Poshak
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Hoenig, Sebastian
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Mchardy, Ian
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Middleton, Matthew
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Shankar, Francesco
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Calderone, Giorgio
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Knigge, Christian
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Matthews, James
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Buckland, Rachel
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Hryniewicz, Krzysztof
c3e5e6c6-7ec7-41e2-89db-5ce7a840084b
Sivakoff, Gregory
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Dai, Xinyu
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Richardson, Kayleigh
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Riley, Jack
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Gray, James
ef2baeb0-a60b-4ae6-9d76-48d6208de51d
La Franca, Fabio
abbb3d3c-c4e3-4e73-920a-c6c183698ed2
Altamirano, Diego
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Croston, Judith
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Gandhi, Poshak
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Hoenig, Sebastian
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Mchardy, Ian
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Middleton, Matthew
cb640432-15c4-41dc-8420-e8594eab1ffe

Shankar, Francesco, Calderone, Giorgio, Knigge, Christian, Matthews, James, Buckland, Rachel, Hryniewicz, Krzysztof, Sivakoff, Gregory, Dai, Xinyu, Richardson, Kayleigh, Riley, Jack, Gray, James, La Franca, Fabio, Altamirano, Diego, Croston, Judith, Gandhi, Poshak, Hoenig, Sebastian, Mchardy, Ian and Middleton, Matthew (2016) The optical-UV emissivity of quasars: dependence on black hole mass and radio loudness. The Astrophysical Journal, 818 (1), 1-6. (doi:10.3847/2041-8205/818/1/L1).

Record type: Article

Abstract

We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 ≤ z ≤ 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) α3000 continuum slopes (Lν ∝  να at 3000 Å) with increasing black hole mass, bluer α3000 with increasing luminosity at 3000 Å, and bluer α3000 with increasing spin of the black hole, when all other parameters are held fixed. We find no clear evidence for any of these predictions in the data. In particular, we find the following. (i) α3000 shows no significant dependence on black hole mass or luminosity. Dedicated Monte Carlo tests suggest that the substantial observational uncertainties in the black hole virial masses can effectively erase any intrinsic dependence of α3000 on black hole mass, in line with some previous studies. (ii) The mean slope α3000 of radio-loud sources, thought to be produced by rapidly spinning black holes, is comparable to, or even redder than, that of radio-quiet quasars. Indeed, although quasars appear to become more radio loud with decreasing luminosity, we still do not detect any significant dependence of α3000 on radio loudness. The predicted mean α3000 slopes tend to be bluer than in the data. Disk models with high inclinations and dust extinction tend to produce redder slopes closer to empirical estimates. Our mean α3000 values are close to the ones independently inferred at z < 0.5, suggesting weak evolution with redshift, at least for moderately luminous quasars.

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Accepted/In Press date: 21 December 2015
e-pub ahead of print date: 1 February 2016
Published date: 1 February 2016
Organisations: Physics & Astronomy

Identifiers

Local EPrints ID: 394517
URI: http://eprints.soton.ac.uk/id/eprint/394517
ISSN: 1538-4357
PURE UUID: 0a47e9d6-b1cd-4b47-b169-8722eebf556d
ORCID for Diego Altamirano: ORCID iD orcid.org/0000-0002-3422-0074
ORCID for Poshak Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

Catalogue record

Date deposited: 19 May 2016 14:41
Last modified: 17 Dec 2019 01:35

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Contributors

Author: Giorgio Calderone
Author: James Matthews
Author: Rachel Buckland
Author: Krzysztof Hryniewicz
Author: Gregory Sivakoff
Author: Xinyu Dai
Author: Kayleigh Richardson
Author: Jack Riley
Author: James Gray
Author: Fabio La Franca
Author: Judith Croston
Author: Poshak Gandhi ORCID iD
Author: Ian Mchardy
Author: Matthew Middleton

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