J/ApJ/758/129ivo://CDS.VizieR/J/ApJ/758/129doi:10.26093/cds/vizier.17580129CDSXue Y.Q.Wang S.X.Brandt W.N.Luo B.Alexander D.M.Bauer F.E.,Comastri A.Fabian A.C.Gilli R.Lehmer B.D.Schneider D.P.,Vignali C.Young M.2014-08-27T15:34:57Z2014-08-08T10:43:13ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiredshiftedinfrared-photometryx-ray-sourcesabsolute-magnitudesurveysUsing the 4Ms Chandra Deep Field-South (CDF-S) survey, we have identified a sample of 6845 X-ray-undetected galaxies that dominates the unresolved {approx}20%-25% of the 6-8keV cosmic X-ray background (XRB). This sample was constructed by applying mass and color cuts to sources from a parent catalog based on GOODS-South Hubble Space Telescope z-band imaging of the central 6' radius area of the 4Ms CDF-S. The stacked 6-8keV detection is significant at the 3.9{sigma} level, but the stacked emission was not detected in the 4-6keV band, which indicates the existence of an underlying population of highly obscured active galactic nuclei (AGNs). Further examinations of these 6845 galaxies indicate that the galaxies on the top of the blue cloud and with redshifts of 1<~z<~3, magnitudes of 25<~z_850_<~28, and stellar masses of 2x10^8^<~M_{sstarf}_/M_{sun}_<~2x10^9^ make the majority contributions to the unresolved 6-8keV XRB. Such a population is seemingly surprising given that the majority of the X-ray-detected AGNs reside in massive (>~10^10^M_{sun}_) galaxies. We discuss constraints upon this underlying AGN population, supporting evidence for relatively low mass galaxies hosting highly obscured AGNs, and prospects for further boosting the stacked signal.2012ApJ...758..129Xhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/758/129CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2014)II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)J/ApJS/207/24 : GOODS-S CANDELS multiwavelength catalog (Guo+, 2013)J/A+A/556/A114 : AGNs in XMM deep survey in CDF-S (Castello-Mor+, 2013)J/A+A/555/A42 : The XMM-CDFS catalogues (Ranalli+, 2013)J/MNRAS/420/2190 : ECDFS sources with radio counterparts (Vattakunnel+, 2012)J/ApJ/748/124 : AGN X-ray variability in the 4Ms catalog (Young+, 2012)J/A+A/534/A110 : Type-2 AGN from XMM-COSMOS bolometric output (Lusso+, 2011)J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)J/ApJ/742/61 : Phot. redshift of AGNs from XMM- and C-COSMOS (Salvato+ 2011)J/ApJ/742/3 : Photometric catalogs for ECDF-S and CDF-N (Rafferty+, 2011)J/ApJ/740/37 : Obscured AGN at z~0.5-1 in the CDFS (Luo+, 2011)J/ApJS/191/124 : Opt. spectroscopy of ECDF-S X-ray sources (Silverman+, 2010)J/ApJS/189/270 : MUSYC optical imaging in ECDF-S (Cardamone+, 2010)J/ApJS/187/560 : Photometric redshifts of the 2Ms CDF-S (Luo+, 2010)J/ApJ/720/368 : Color-magnitude relations of galaxies in CDFs (Xue+, 2010)J/ApJ/708/137 : Broad-line AGNs in zCOSMOS survey (Merloni+, 2010)J/MNRAS/398/1165 : AGN in nearby galaxies (Goulding+, 2009)J/A+A/507/1277 : Multiwavelength phot. of CDFS X-ray sources (Brusa+, 2009)J/A+A/497/81 : Variability-selected AGN in CDFS (Boutsia+, 2009)J/ApJ/693/1713 : Spectroscopy of X-ray sources in ECDF-S (Treister+, 2009)J/ApJS/179/19 : CDFS survey: 2 Ms source catalogs (Luo+, 2008)J/AJ/135/1505 : CDFs AGNs X-ray power-law photon index (Saez+, 2008)J/A+A/488/73 : Variability-selected AGN in Chandra DFS (Trevese+, 2008)J/A+A/466/823 : Hard 2-10kev X-ray selected sources (Georgantopoulos+, 2007)J/A+A/451/457 : X-ray properties of AGN in CDFS (Tozzi+, 2006)J/ApJ/640/167 : AGNs and ULIRGs in the CDF-South (Alonso-Herrero+, 2006)J/AJ/131/2373 : Extended Chandra Deep Field-South survey (Virani+, 2006)J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)J/ApJS/155/271 : CDF-South: Optical spectroscopy (Szokoly+, 2004)J/ApJS/155/73 : Photometric redshifts of X-ray sources in CDF-S (Zheng+, 2004)J/AJ/126/539 : The Chandra Deep Fields North and South (Alexander+, 2003)J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/758/129https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/758/129http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/758/129https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/758/129https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/758/129http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/758/129GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/758/129/table4 (Derived properties for the sources in sample A)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/758/129/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/758/129/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/758/129/table4?GETtext/xml+votable180.050000true53.00981-27.837180.0055555555555555566/359351.1796835550914393e-19 2.1189193140583396e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/758/129?format=asciiX-rayOpticalInfrareddefaultJ/ApJ/758/129/table4Derived properties for the sources in sample ArecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/18035] Source running sequence numbermeta.id;meta.mainintRAJ2000[53.009/53.23] Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-27.91/-27.7] Declination (J2000)degpos.eq.dec;meta.mainzsp[0.07/5.9]? Spectroscopic redshiftsrc.redshiftfloatnullablezph[0.03/7] Photometric redshiftsrc.redshiftfloate_zph1-{sigma} lower limit on zphstat.errorfloatE_zph1-{sigma} upper limit on zphstat.error;stat.maxfloatUMag[-25.1/-9] Rest-frame absolute U-band Vega magnitude (1)magphys.magAbs;em.opt.UfloatBMagRest-frame absolute B-band Vega magnitude (1)magphys.magAbs;em.opt.BfloatVMagRest-frame absolute V-band Vega magnitude (1)magphys.magAbs;em.opt.VfloatredMag[-26.6/-13.6] Reddest rest-frame absolute Vega magnitude (1)magphys.magAbs;em.opt.Rfloatf_redMag[1/7] Flag of reddest rest-frame coverage (2)meta.codeintMass[5.8/13] Log stellar-mass estimate adopted herelog(solMass)arith.zpfloatMassFLog stellar-mass estimate calculated by FASTlog(solMass)phys.massfloatYmag[16.6/28.9]? CANDELS HST/WFC3 F105W Y-band AB magnitudemagphot.mag;em.IR.Hfloatnullablee_Ymag[0/1]? 1-{sigma} uncertainty in Ymagmagstat.error;phot.mag;em.opt.BfloatnullableJmag[16.5/29]? CANDELS HST/WFC3 F125W J-band AB magnitudemagphot.mag;em.IR.Hfloatnullablee_Jmag? 1-{sigma} uncertainty in Jmagmagstat.error;phot.mag;em.IR.JfloatnullableHmag[16.4/29.8]? CANDELS HST/WFC3 F160W H-band AB magnitudemagphot.mag;em.IR.Hfloatnullablee_Hmag? 1-{sigma} uncertainty in Hmagmagstat.error;phot.mag;em.IR.HfloatnullableCANDELSCross-match within 0.5" with Guo+, 2013, Cat. J/ApJS/207/24meta.ref.urlintnullable