Deficit of Hot Dust in Low-redshift Active Galactic Nuclei

Abstract

We assemble a broadband spectral energy distribution (SED) ranging from the optical to the mid-infrared of nearby active galactic nuclei (AGNs) at z < 0.4. The SED fitting analysis is performed using semiempirical templates derived from Palomar-Green quasars to classify the sample into normal, warm-dust-deficient (WDD), and hot-dust-deficient (HDD) AGNs. Kolmogorov–Smirnov tests reveal that HDD AGNs exhibit higher AGN luminosity on average than normal and WDD AGNs. The HDD fraction, on the other hand, is only weakly correlated with the black hole mass and inversely correlated with the Eddington ratio. By fixing the other parameters, we conclude that the HDD fraction is primarily connected with the AGN luminosity. This implies that there is a causal connection between the covering factor of the hot dust component and AGN luminosity, possibly due to the sublimation of the innermost dust or the thickening of the intervening gas in the broad-line region. Analysis of the outflow properties traced by the wing of [O iii]λ5007 suggests that outflows may be related to the formation and maintenance of the hot dust component. Finally, we demonstrate through comparison with previous studies that the classification of HDD AGNs requires careful subtraction of the host galaxy light.