The evolution of dusty torus covering factor in quasars

Abstract

We have assembled a large sample of 5996 quasars at redshift 2.0=< z <= 2.4 (high-z) or 0.7=< z <= 1.1 (low-z) from SDSS data release nine and seven quasar catalogs. The spectral energy distribution (SED) of quasars were constructed by collecting WISE, UKIDSS, and GALEX photometric data in addition to SDSS, from which the IR luminosity at 1-7 μm and bolometric luminosity at 1100 Å- 1 μm were calculated. A red tail is clearly seen in the distributions of the spectral index in 1100 Å- 1 μm both for high-z and low-z sources, which is likely due to red or reddened quasars. The covering factor of dusty torus is estimated as the ratio of the IR luminosity to the bolometric luminosity. We found significant anti-correlations between the covering factor and bolometric luminosity, in both high-z and low-z quasars, however they follow different tracks. At overlapped bolometric luminosity, the covering factor of high-z quasars are systematically larger than those of low-z quasars, implying an evolution of covering factor with redshift.

22 pages, 6 figures, accepted to ApJ, text slightly revised

References in corpus (13)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The Baryon Oscillation Spectroscopic Survey of SDSS-III
• A Catalog of Quasar Properties from SDSS DR7
• Absorption Properties and Evolution of Active Galactic Nuclei
• The Sloan Digital Sky Survey quasar catalog: ninth data release
• Dust covering factor, silicate emission and star formation in luminous QSOs
• The distribution of silicate strength in Spitzer spectra of AGNs and ULIRGs
• Probabilistic Cross-Identification of Astronomical Sources
• The Toroidal Obscuration of Active Galactic Nuclei
• Spectral Energy Distributions of Type 1 AGN in the COSMOS Survey I - The XMM-COSMOS Sample
• IR-derived covering factors for a large sample of quasars from WISE-UKIDSS-SDSS
• The GALEX Time Domain Survey I. Selection and Classification of Over a Thousand UV Variable Sources
• The Covering Factor of Warm Dust in Quasars: View from WISE All-Sky Data Release

Cited by in corpus (17)

• On the jet properties of the gamma-ray loud active galactic nuclei
• Dust-Deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission
• Determining the covering factor of Compton-thick active galactic nuclei with NuSTAR
• Luminosity and Redshift Dependence of the Covering Factor of AGNs viewed with WISE and SDSS
• How does the Polar Dust affect the Correlation between Dust Covering Factor and Eddington Ratio in Type 1 Quasars Selected from the Sloan Digital Sky Survey Data Release 16?
• Differences in Halo-Scale Environments between Type 1 and Type 2 AGNs at Low Redshift
• The WISSH quasars project XI. The mean Spectral Energy Distribution and Bolometric Corrections of the most luminous quasars
• An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?
• The luminosity dependence of quasar UV continuum slope: dust extinction scenario
• Dusty plasma in active galactic nuclei
• Quasars as standard candles VI: spectroscopic validation of the cosmological sample
• Viewing angle observations and effects of evolution with redshift, black hole mass, and Eddington ratio in quasar based cosmology
• The near-infrared SED of blue quasars: what drives the evolution of the dusty torus?
• Viewing angle effects in quasar application to cosmology
• The disk-torus system in active galactic nuclei: possible evidence of highly spinning black holes
• The optical-infrared relation for active galactic nuclei: The role of contaminations
• The properties of the obscuring material of an AGNs sample from mid-IR and X-ray simultaneous fitting