Covering factor of warm dust in quasars

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_.