NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-05-23 T15:08:24 PDT
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For refcode 2015ApJ...814...11T:
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2015ApJ...814...11T A New Sample of Obscured AGNs Selected from the XMM-Newton and AKARI Surveys Terashima, Yuichi; Hirata, Yoshitaka; Awaki, Hisamitsu; Oyabu, Shinki; Gandhi, Poshak; Toba, Yoshiki; Matsuhara, Hideo Abstract. We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 micron) sources located at | b| \gt 10^ deg to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2--4.5 keV and 4.5--12 keV bands > -0.1 and (2) EPIC-PN count rate (CR) in the 0.2--12 keV to infrared flux ratio CR/{F}_90_\lt 0.1 or CR/{F}_18_\lt 1, where F_18_ and F_90_ are infrared fluxes at 18 and 90 micron in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of {N}_{{H_}} ~ 10^22--24^ cm^-2^, a very flat continuum, or a strong Fe--K emission line with an equivalent width of \gt 700 {{eV}} is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18 micron condition is used. Of the 26 objects, 4 are optically classified as an H II nucleus and are new "elusive AGNs" in which star formation activity likely overwhelms AGN emission in the optical and infrared bands. Key words: galaxies: active, infrared: galaxies, X-rays: galaxies
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