Evolutionary Consequences of Dusty Tori in Active Galactic Nuclei

Abstract

Deep surveys of {\em Chandra} and {\em HST} (Hubble Space Telescope) show that active galactic nucleus (AGN) populations are changing with hard X-ray luminosities. This arises an interesting question whether the dusty torus is evolving with the central engines. We assemble a sample of 50 radio-quiet PG quasars to tackle this problem. The covering factors of the dusty tori can be estimated from the multiwavelength continuum. We find they are strongly correlated with the hard X-ray luminosity. Interestingly this correlation agrees with the fraction of type II AGNs discovered by {\em Chandra} and {\em HST}, implying strong evidence for that the AGN population changing results from the evolution of the tori. We also find that the frequencies of the dips around 1$\mu$m in the continuum correlate with the covering factors in the present sample, indicating the dip frequencies are adjusted by the covering factors. In the scenario of fueling black hole from the torus, the covering factor is a good and the dip frequency is a potential indicator of the torus evolution.

4 pages in emulateapj5.sty. Accepted by ApJ Letters

References in corpus (17)

• Cosmological Evolution of the Hard X-ray AGN Luminosity Function and the Origin of the Hard X-ray Background
• Dust Emission from Active Galactic Nuclei
• The Cosmic Evolution of Hard X-ray Selected Active Galactic Nuclei
• X-ray Spectra of a large sample of Quasars with ASCA
• XMM-Newton EPIC observations of 21 low-redshift PG quasars
• X-ray Observations of Optically-Selected, Radio-Quiet Quasars I: The ASCA results
• The Changing AGN Population
• Obscured AGN and the X-ray, Optical and Far-Infrared Number Counts of AGN in the GOODS Fields
• Elusive Active Galactic Nuclei
• High Spatial Resolution Imaging of NGC 1068 in the Mid Infrared
• An X-ray Baldwin effect for the narrow Fe K-alpha lines observed in Active Galactic Nuclei
• Narrow Iron K$\alpha$ Lines in Active Galactic Nuclei: Evolving Populations?
• The X-ray Background and AGNs
• An Optical Catalog of the Chandra Large Area Synoptic X-ray Survey Sources
• On the dust tori in Palomar-Green quasars
• A Single Intrinsic Luminosity Function for Both Type-I and Type-II Active Galactic Nuclei
• Collisions among Clouds inside Dusty Torus in Active Galactic Nuclei: Observational Consequences

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