J/A+AS/123/529ivo://CDS.VizieR/J/A+AS/123/529CDSGosset E.Moreau O.Surdej J.1998-09-10T15:20:19Z1998-09-10T15:19:52ZCDS support team

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

cds-question@unistra.frquasarsvisible-astronomyWide-band photometryredshiftedWe describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates we re-selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates were selected on the basis of their U image being too bright. The spectroscopic identification of the primary candidates led to the discovery of 59 bona fide quasars (out of which 6 were previously known). The Palomar Schmidt plate was digitised using the MAMA measuring machine and the outcoming data reduced using ad hoc procedures. A photometric calibration allowed us to derive values for the limiting magnitudes and for the U-B index selection threshold of the survey. A catalogue containing 60 quasars is presented with accurate positions, magnitudes and additional information such as redshifts. We studied the spatial distribution of the objects and detected, for the quasars of our sample, a significant deviation from randomness in the form of a propensity to cluster in pairs on the celestial sphere with a typical scale of about 10arcmin. We also formally detected a tendency towards a 3-D clustering, but this result is induced by a single pair of quasars. A forthcoming paper will deal with a similar work performed in a field around NGC 520; the latter field is located directly to the North of the present one and slightly overlaps it.1997A&AS..123..529Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+AS/123/529CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+AS/123/529https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+AS/123/529http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+AS/123/529https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+AS/123/529https://vizier.iucaa.in/viz-bin/votable?-source=J/A+AS/123/529http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+AS/123/529GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+AS/123/529/table6 (Catalogue of quasars and quasar candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+AS/123/529/table6?https://vizier.iucaa.in/viz-bin/conesearch/J/A+AS/123/529/table6?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+AS/123/529/table6?GETtext/xml+votable180.050000true17.47654170.63680560.005555555555555556https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+AS/123/529?format=asciiOpticaldefaultJ/A+AS/123/529/table6Catalogue of quasars and quasar candidatesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainu_RAs[:] ":" slightly less precise valuemeta.code.errorcharDEJ2000Declination signpos.eq.dec;meta.mainu_DEs[:] ":" slightly less precise valuemeta.code.errorcharz? Redshiftsrc.redshiftdoublenullableu_z[?:] ":" uncertain value "?" very uncertain valuemeta.code.errorcharNameObject name (1)meta.id;meta.maincharP/S[PS] Primary (P) or secondary (S) candidatemeta.notecharn_P/S[*] * when the spectrum of the object is available in fig.2 of the paper.meta.notecharNGC450? Internal identification number in the present survey (NGC450 # "NGC450")meta.idintnullablen_NGC450[*] Flag indicating a note in notes.dat filemeta.notecharNGC520? Identification number in the NGC 520 survey (NGC520 # 'NGC520')meta.idintnullablem_NGC520[B] Multiplicity index on NGC520meta.code.multipcharl_BmagLimit flag on Bmagmeta.code.errorcharBmagB magnitudemagphot.mag;em.opt.Bfloatu_BmagUncertainty flag on Bmagmeta.code.errorcharl_UmagLimit flag on Umagmeta.code.errorcharUmagU magnitudemagphot.mag;em.opt.Ufloatu_UmagUncertainty flag on Umagmeta.code.errorcharl_U-BLimit flag on U-Bmeta.code.errorcharU-BU-B colour indexmagphot.color;em.opt.U;em.opt.Bfloatu_U-BUncertainty flag on U-Bmeta.code.errorcharSpectSpectroscopy (2)meta.codecharJ/A+AS/123/529/notesIndividual notesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNGC450NGC450 internal designationmeta.id;meta.mainintNoteText of the notemeta.notechar