The covering factor of warm dust in quasars: a view from the Wide-field Infrared Survey Explorer All-Sky Data Release

By combining newly obtained infrared photometric data from the All-Sky Data Release of the Wide-field Infrared Survey Explorer with spectroscopic data from the Seventh Data Release of the Sloan Digital Sky Survey, we study the covering factor of warm dust (CFWD) for a large quasar sample, as well as...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2013-04, Vol.430 (4), p.3445-3452
Main Authors: Ma, Xiang-Cheng, Wang, Ting-Gui
Format: Article
Language:English
Subjects:
Anisotropy
Astrophysics
Correlation analysis
Luminosity
Star & galaxy formation
Ultraviolet radiation
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Summary:By combining newly obtained infrared photometric data from the All-Sky Data Release of the Wide-field Infrared Survey Explorer with spectroscopic data from the Seventh Data Release of the Sloan Digital Sky Survey, we study the covering factor of warm dust (CFWD) for a large quasar sample, as well as the relations between CFWD and other physical parameters of quasars. We find a strong correlation between the flux ratio in the mid-infrared to near-ultraviolet and the slope of the near-ultraviolet spectra, which is interpreted as a dust extinction effect. After correcting for dust extinction utilizing the above correlation, we examine the relations between CFWD and active galactic nucleus properties: bolometric luminosity (L bol), black hole mass (M BH) and Eddington ratio (L/L Edd). We confirm the anticorrelation between CFWD and L bol. Further, we find that CFWD is anticorrelated with M BH but is independent of L/L Edd. Radio-loud quasars are found to follow the same correlations as radio-quiet quasars. Monte Carlo simulations show that the anisotropy of the UV-optical continuum of the accretion disc can have a significant effect, but is not likely to dominate the CFWD-L bol correlation.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stt143