J/A+A/708/A157ivo://CDS.VizieR/J/A+A/708/A157CDSGuo X.Gu Q.Fang G.Lu S.Lyu F.Chen Y.Ding N.Zhang M.Yu X.,Wang H.2026-05-04T07:43:19Z2026-04-03T11:39:21ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fractive-galactic-nucleix-ray-sourcesCompton-thick active galactic nuclei (CT-AGNs), defined by column density N_H_>=1.5x10^24^cm^-2^, are so heavily absorbed that their X-ray emission is often feeble, even undetectable by X-ray instruments. Nevertheless, their radiation is expected to be a substantial contributor to the cosmic X-ray background (CXB), predicting that CT-AGNs should comprise at least 30% of the total AGN population. In the Cosmological Evolution Survey (COSMOS), the identified CT-AGN fraction falls far below theoretical expectations, indicating that a substantial population of CT-AGNs is hidden due to their low photon counts or their flux below the current flux limits of X-ray instruments. This work focuses on identifying CT-AGNs hidden in mid-infrared (MIR)-selected AGNs. First, we selected a sample of 1,104 MIR-selected AGNs that were covered but individually undetected by X-ray. Next, we reduced the X-ray data in the COSMOS and analyzed multiwavelength data in our sample to derive the key physical parameters required for CT-AGN identification. Using MIR diagnostics, we first find out 7 to 23 CT-AGN candidates. Their subsequent X-ray stacking analysis reveals a clear detection at >3sigma significance in the soft band and only >1sigma significance in the hard band. We fit the stacked soft- and hard-band fluxes with a physical model and confirm that these sources are absorbed by Compton-thick material. However, CT-AGNs constitute only 2.1% (23/1104) of our sample, significantly below the fraction predicted by CXB synthesis models, indicating that a considerable population of CT-AGNs remains missed by our selection. A comparison of host-galaxy properties between CT-AGNs and non-CT-AGNs reveals no significant differences.2026A&A...708A.157Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/708/A157CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/258/11 : The COSMOS2020 catalog (Weaver+, 2022)J/A+A/694/A241 : Identifying CT-AGNs in the COSMOS. I. (Guo+, 2025)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/708/A157https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/708/A157http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/708/A157https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/708/A157https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/708/A157http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/708/A157GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/708/A157/tablea1 (Parameters adopted for CT-AGN selection from the MIR-selected AGN and the identified CT-AGNs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/708/A157/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/708/A157/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/708/A157/tablea1?GETtext/xml+votable180.050000true149.6744051.624943890.0055555555555555565/6814 6/27245 27247 27344https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/708/A157?format=asciiX-raydefaultJ/A+A/708/A157/tablea1Parameters adopted for CT-AGN selection from the MIR-selected AGN and the identified CT-AGNsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIDs from the COSMOS2020 FARMER catalog (1)meta.id;meta.mainintRAJ2000Right ascension (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (1)degpos.eq.dec;meta.mainzRedshift (1)src.redshiftdoubleB3The background counts of the source within a radius of 3 arcsecinstr.backgroundintTexpThe exposure time of the sourcelog(s)time.duration;obs.exposuredoubleFlux2-10The upper limit of 2-10keV fluxlog(1e-07W.cm**-2)phot.flux;em.X-raydoublelogL2-10? Log of the upper limit of 2-10keV luminositylog(1e-07W)phys.luminosity;em.X-raydoublenullablelogL6um? Log of 6um luminosity for an AGN in the rest-framelog(1e-07W)phys.luminosity;em.IRdoublenullablealphaAGN? Confidence of AGN components for SED fittingstat.fit.paramdoublenullablelogMstar? Log of the stellar masslog(solMass)phys.massdoublenullablelogSFR? Log of the star formation ratelog(solMass.yr**-1)meta.iddoublenullableCTflag[0/1] CT-AGN flag; 1 = CT-AGN identifiedmeta.codeint