NuSTAR Reveals Extreme Absorption in z < 0.5 Type 2 Quasars

Abstract

The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z<1, the X-ray spectra can only be reliably characterized using broad-band measurements which extend to energies above 10 keV. Using the hard X-ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (NH > 1.5e24 cm^-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z<0.5, have observed [OIII] luminosities in the range 8.4 < log (L_[OIII]/L_solar) < 9.6, and show evidence for extreme, Compton-thick absorption when indirect absorption diagnostics are considered. Amongst the nine candidate CTQSO2s, five are detected by NuSTAR in the high energy (8-24 keV) band: two are weakly detected at the ~ 3 sigma confidence level and three are strongly detected with sufficient counts for spectral modeling (>~ 90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic AGN properties are feasible, and we measure column densities ~2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ~10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of f_CT = 36^{+14}_{-12} %, although higher fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable.

19 pages, 13 figures, 5 tables. Accepted for publication in ApJ

References in corpus (27)

• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• Obscuration-dependent evolution of Active Galactic Nuclei
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• Half of the Most Luminous Quasars May Be Obscured: Investigating the Nature of WISE-Selected Hot, Dust-Obscured Galaxies
• Type II Quasars from the Sloan Digital Sky Survey: V. Imaging host galaxies with the Hubble Space Telescope
• The X-Ray to Mid-Infrared Relation of AGN at High Luminosity
• Reliable Identification of Compton-thick Quasars at z~2: Spitzer Mid-IR spectroscopy of HDF-oMD49
• A large population of mid-infrared selected, obscured active galaxies in the Bootes field
• NuSTAR and XMM-Newton Observations of Luminous, Heavily Obscured, WISE-Selected Quasars at z ~ 2
• The NuSTAR View of Nearby Compton-thick AGN: The Cases of NGC 424, NGC 1320 and IC 2560
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• Radiation pressure and absorption in AGN: results from a complete unbiased sample from Swift
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• Weak Hard X-ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-ray Weakness
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• The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
• Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios
• Low Resolution Spectral Templates For Galaxies From 0.2 -- 10 microns
• The quest for Type 2 quasars: Chandra observations of luminous obscured quasars in the Sloan Digital Sky Survey
• Delving Into X-ray Obscuration of Type 2 AGN, Near and Far
• NuSTAR J033202-2746.8: direct constraints on the Compton reflection in a heavily obscured quasar at z~2
• A Compton thick AGN in the barred spiral NGC 4785
• The space density of Compton-thick AGN at z~0.8 in the zCOSMOS-Bright Survey
• The most obscured AGN in the COSMOS field

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