J/A+A/542/A16ivo://CDS.VizieR/J/A+A/542/A16doi:10.26093/cds/vizier.35420016CDSRanalli P.Comastri A.Zamorani G.Cappelluti N.Civano F.,Georgantopoulos I.Gilli R.Schinnerer E.Smolcic V.Vignali C.2017-06-01T08:52:24Z2012-05-29T08:50:52ZCDS support team

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

cds-question@unistra.frradio-galaxiesactive-galactic-nucleix-ray-sourcesredshiftedX-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008ApJS..177...14S) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolcic et al. (2008ApJS..177...14S) is such that ~30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be much lower among X-ray undetected sources. Indeed, the analysis of the stacked spectrum of undetected sources shows, consistently, strongly different properties between the AGN and galaxy samples. X-ray based selection criteria are then used to refine both samples. The radio/X-ray luminosity correlation for star forming (SF) galaxies is found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some evolution of the ratio may be possible for sources at high redshift or high luminosity, tough it is likely explained by a bias arising from the radio selection. Finally, we discuss the X-ray number counts of star forming galaxies from the VLA- and C-COSMOS surveys according to different selection criteria, and compare them to the similar determination from the Chandra Deep Fields. The classification scheme proposed here may find application in future works and surveys.2012A&A...542A..16Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/542/A16CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)J/ApJS/172/46 : VLA-COSMOS survey. II. (Schinnerer+, 2007)J/ApJS/188/384 : The VLA-COSMOS survey. IV. (Schinnerer+, 2010https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/542/A16https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/542/A16http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/542/A16https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/542/A16https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/542/A16http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/542/A16GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/542/A16/galaxies (Catalogue of radio-selected SF/AGN candidates with an X-ray detection in C-COSMOS)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/542/A16/galaxies?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/542/A16/galaxies?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/542/A16/galaxies?GETtext/xml+votable180.050000true149.68691672.18341670.0055555555555555565/6814 6/27247https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/542/A16?format=asciiX-rayOpticalRadiodefaultJ/A+A/542/A16/galaxiesCatalogue of radio-selected SF/AGN candidates with an X-ray detection in C-COSMOSl_FSLimit flag on FSmeta.code.errorcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCOSMOSVLAVLA name (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharCXOCChandra name (JHHMMSS.s+DDMMSS)meta.idcharSeqChandra ID from Elvis et al. (2009, Cat. J/ApJS/184/158)meta.idintzSpectroscopic redshiftsrc.redshiftfloatn_z[a] a for photometric redshiftmeta.notecharFSX-ray flux in soft band (0.5-2keV, erg/cm2/s)mW.m**-2phot.flux;em.X-raydoublel_FHLimit flag on FHmeta.code.errorcharFHX-ray flux in hard band (2-10keV, erg/cm2/s)mW.m**-2phot.flux;em.X-raydoublel_LSLimit flag on LSmeta.code.errorcharLSX-ray luminosity in soft band (0.5-2keV, erg/s)1e-07Wphys.luminosity;em.X-raydoublel_LHLimit flag on LHmeta.code.errorcharLHX-ray luminosity in hard band (2-10keV, erg/s)1e-07Wphys.luminosity;em.X-raydoubleHRHardness ratio (H-S)/(H+S)phot.flux;arith.ratiofloatl_X/OLimit flag on X/Ometa.code.errorcharX/OX-ray/optical flux ratio (1)phot.flux;arith.ratiofloatl_qLimit flag on qmeta.code.errorcharqX-ray/radio flux ratio, q=Log(FS/S1.4GHz)phot.flux;arith.ratiofloatRclSimbad column added by the CDSmeta.code.classcharOcl[T12 EAL] Optical classification (2)meta.code.classcharXcl[1/3] Classification according to this paper (1=agrees with radio class) (3)meta.code.classint_RAPosition, derived from the COSMOSVLA name (right ascension part)degpos.eq.ra;meta.main_DEPosition, derived from the COSMOSVLA name (declination part)degpos.eq.dec;meta.main