J/ApJ/748/124ivo://CDS.VizieR/J/ApJ/748/124doi:10.26093/cds/vizier.17480124CDSYoung M.Brandt W.N.Xue Y.Q.Paolillo M.Alexander D.M.Bauer F.E.,Lehmer B.D.Luo B.Shemmer O.Schneider D.P.Vignali C.2017-10-12T13:00:24Z2013-11-29T07:45:06ZCDS support team

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

cds-question@unistra.frx-ray-sourcesredshiftedactive-galactic-nucleiThe 4 Ms Chandra Deep Field-South (CDF-S) and other deep X-ray surveys have been highly effective at selecting active galactic nuclei (AGNs). However, cosmologically distant low-luminosity AGNs (LLAGNs) have remained a challenge to identify due to significant contribution from the host galaxy. We identify long-term X-ray variability (~month-years, observed frame) in 20 of 92 CDF-S galaxies spanning redshifts z{approx}0.08-1.02 that do not meet other AGN selection criteria. We show that the observed variability cannot be explained by X-ray binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole (SMBH). The variable galaxies are not heavily obscured in general, with a stacked effective power-law photon index of {Gamma}_stack_{approx}1.93+/-0.13, and are therefore likely LLAGNs. The LLAGNs tend to lie a factor of {approx}6-80 below the extrapolated linear variability-luminosity relation measured for luminous AGNs.2012ApJ...748..124Yhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/748/124CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2013)II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)J/A+A/555/A42 : The XMM-CDFS catalogues (Ranalli+, 2013)J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)J/ApJ/720/368 : Color-magnitude relations of galaxies in CDFs (Xue+, 2010)J/A+A/507/1277 : Multiwavelength phot. of CDFS X-ray sources (Brusa+, 2009)J/ApJS/179/19 : CDFS survey: 2 Ms source catalogs (Luo+, 2008)J/ApJ/640/167 : AGNs and ULIRGs in the CDF-South (Alonso-Herrero+, 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/748/124https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/748/124http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/748/124https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/748/124https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/748/124http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/748/124GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/748/124/table2 (X-ray properties of CDF-S galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/748/124/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/748/124/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/748/124/table2?GETtext/xml+votable180.050000true53.026667-27.7911110.0055555555555555566/35935https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/748/124?format=asciiX-rayOpticaldefaultJ/ApJ/748/124/table2X-ray properties of CDF-S galaxiesU-V[-0.91/1.55] The (U-V) color indexmagphot.color;em.opt.U;em.opt.VfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintXID[66/679] Sequence number (1)meta.idintf_XID[V] V = long-term X-ray variable source (20 sources); blank = non-variable CDF-S galaxymeta.codecharNameCDF-S name (HHMMSS.ss+DDMMSS.s; J2000; <CXOCDFS JHHMMSS.s+DDMMSS> in Simbad)meta.id;meta.maincharz[0.04/2.01] Redshift from litterature (see section 2)src.redshiftfloatf_z[ps] Redshift measurement: s=spectro, p=photometa.codecharl_NCts[0/1]? Upper 3{sigma} limit flag on NCts (2)meta.code.errorintnullableNCts[19/608.9] Total net 0.5-8.0 keV countsctphot.count;em.X-rayfloatLx[38.9/42.4] Log 0.5-8 keV, rest frame X-ray luminosity; in erg/slog(1e-07W)phys.luminosity;em.X-rayfloatGeff[0.5/3] Effective photon index {Gamma}_eff_ (3)spect.indexfloatE_Geff[0/3.5] Upper confidence interval on Geffstat.error;stat.maxfloate_Geff[0/2.6] Lower confidence interval on Geffstat.errorfloatchi2[0/11.2] Variability statisticstat.fit.paramfloatPchi2[0/1] Probability variability is due to chancesrc.varfloatR[1.2/9.3] Maximum-to-minimum flux ratiophot.mag;arith.ratiofloatnxs[-0.3/0.7] Excess variancestat.variancefloate_nxs[0.01/0.5] Error in nxsstat.errorfloatnxsc[-0.4/2] Excess variance corrected for sampling biasstat.variancefloate_nxsc[0.01/1.5] Error in nxscstat.errorfloatSFR[0.01/541] Xue et al. 2010, Cat. J/ApJ/720/368, Star Formation RatesolMass/yrphys.SFRfloatMstar[0.002/62] Stellar mass, from Xue et al. 2010, Cat. J/ApJ/720/3681e+10solMassphys.massfloat(H/L)XB[0.01/76] High/Low-mass luminosity ratio (4)phys.luminosity;arith.ratiofloatnxsxb[0.0001/0.05] Excess variance expected due to X-ray binary populationstat.variancefloatMvisVisual classification of galaxy morphology (5)meta.code.class;src.morph.typecharVMag[-23.77/-15.77] Absolute V-band magnitudemagphot.mag;em.opt.VfloatcolorColor classification of galaxy morphology (blue or red)src.class.colorcharMclassFinal classification of galaxy morphology (5)meta.code.classcharMBH[4.8/8.6] Logarithm of black hole masslog(solMass)phys.massfloatEdd[-5.7/-1.2] Eddington ratio (6)phys.luminosity;arith.ratiofloatXBL10Cross-match with Xue et al., 2010, Cat. J/ApJ/720/368, within 3"meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from CDF-S names (right ascension part)degpos.eq.ra;meta.main_DEPositions from CDF-S names (declination part)degpos.eq.dec;meta.main