Searching for highly obscured AGN in the XMM-Newton serendipitous source catalog

Abstract

The majority of active galactic nuclei (AGN) are obscured by large amounts of absorbing material that makes them invisible at many wavelengths. X-rays, given their penetrating power, provide the most secure way for finding these AGN. The XMM-Newton serendipitous source catalog is the largest catalog of X-ray sources ever produced; it contains about half a million detections. These sources are mostly AGN. We have derived X-ray spectral fits for very many 3XMM-DR4 sources ($\gtrsim$ 114 000 observations, corresponding to $\sim$ 77 000 unique sources), which contain more than 50 source photons per detector. Here, we use a subsample of $\simeq$ 1000 AGN in the footprint of the SDSS area (covering 120 deg${}^2$) with available spectroscopic redshifts. We searched for highly obscured AGN by applying an automated selection technique based on X-ray spectral analysis that is capable of efficiently selecting AGN. The selection is based on the presence of either a) flat rest-frame spectra; b) flat observed spectra; c) an absorption turnover, indicative of a high rest-frame column density; or d) an Fe K$\alpha$ line with an equivalent width > 500 eV. We found 81 highly obscured candidate sources. Subsequent detailed manual spectral fits revealed that 28 of them are heavily absorbed by column densities higher than 10${}^{23}$ cm${}^{-2}$. Of these 28 AGN, 15 are candidate Compton-thick AGN on the basis of either a high column density, consistent within the 90% confidence level with N${}_{\mathrm{H}}$ $>$10${}^{24}$ cm${}^{-2}$, or a large equivalent width (>500 eV) of the Fe K$\alpha$ line. Another six are associated with near-Compton-thick AGN with column densities of $\sim$ 5$\times$10${}^{23}$ cm${}^{-2}$. A combination of selection criteria a) and c) for low-quality spectra, and a) and d) for medium- to high-quality spectra, pinpoint highly absorbed AGN with an efficiency of 80%.

arXiv comment18 pages, 10 figures, accepted for publication in A&A

References in corpus (35)

• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The Chandra Deep Field-South Survey: 4 Ms Source Catalogs
• The XMM-Newton Serendipitous Survey. V. The Second XMM-Newton Serendipitous Source Catalogue
• X-ray spectral properties of AGN in the Chandra Deep Field South
• Three years Swift-BAT Survey of AGN: reconciling theory and observations?
• The Space Density of Compton Thick AGN and the X-ray Background
• An XMM-Newton spectral survey of 12 micron selected galaxies. I. X-ray data
• X-ray obscuration and obscured AGN in the local universe
• The X-ray nuclei of intermediate-redshift radio sources
• Tracing the cosmic growth of super massive black holes to z ~ 3 with Herschel
• The XMM Deep survey in the CDFS I. First results on heavily obscured AGN
• Constraining the fraction of Compton-thick AGN in the Universe by modelling the diffuse X-ray background spectrum
• Fe-K line probing of material around the AGN central engine with Suzaku
• Mid-infrared properties of X-ray sources in the Extended Groth Strip
• XMM and Chandra measurements of the AGN intrinsic absorption: dependence on luminosity and redshift
• The evolution of the Compton thick fraction and the nature of obscuration for AGN in the Chandra Deep Field South
• The NuSTAR Extragalactic Survey: A First Sensitive Look at the High-Energy Cosmic X-ray Background Population
• The cosmic X-ray background and the population of the most heavily obscured AGNs
• The 1<z<5 Infrared Luminosity Function of Type I Quasars
• The XMM deep survey in the CDFS IV. Candidate Compton-thick AGN
• Prevalence of High X-ray Obscuring Columns among AGN that Host H${}_2$O Masers
• The [OIII] emission line luminosity function of optically selected type-2 AGN from zCOSMOS
• Lifting the Veil on Obscured Accretion: Active Galactic Nuclei Number Counts and Survey Strategies for Imaging Hard X-ray Missions
• NuSTAR Observations of Heavily Obscured Quasars at z ~ 0.5
• XMM-Newton Observations of a Complete Sample of Optically Selected Type 2 Seyfert Galaxies
• Discovery of Probable Relativistic Fe Emission and Absorption in the Cloverleaf Quasar H 1413+117
• Searching for Compton-thick active galactic nuclei at z~0.1
• Searching for mid-IR obscured AGN in the CDF-N
• A Serendipitous XMM Survey of the SDSS: the evolution of the colour-magnitude diagram of X-ray AGN from z=0.8 to z=0.1
• Drilled by the jet? XMM-Newton discovers a Compton-thick AGN in the GPS galaxy Mkn668
• A new technique to efficiently select Compton-thick AGN
• An Archival Chandra and XMM-Newton Survey of Type 2 Quasars
• X-ray absorption in distant type II QSOs
• X-ray colour-colour selection for heavily absorbed AGN
• Red AGN in XMM-Newton/SDSS fields

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• Piercing Through Highly Obscured and Compton-thick AGNs in the Chandra Deep Fields: I. X-ray Spectral and Long-term Variability Analyses
• Swift-XRT follow-up of gravitational wave triggers during the third aLIGO/Virgo observing run
• Where are Compton-thick radio galaxies? A hard X-ray view of three candidates
• The XMM-Newton survey in the H-ATLAS field
• XMMFITCAT: The XMM-Newton spectral-fit database
• Radio observations of four active galactic nuclei hosting intermediate-mass black hole candidates: studying the outflow activity and evolution
• A search for X-ray absorbed sources in the 3XMM catalogue, using photometric redshifts and Bayesian spectral fits
• Compton-thick active galactic nuclei from the 7 Ms observation in the Chandra Deep Field South
• Multi-wavelength observations of the triple-peaked AGN Mrk 622
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