J/ApJ/718/683ivo://CDS.VizieR/J/ApJ/718/683doi:10.26093/cds/vizier.17180683CDSCarraro G.Vazquez R.A.Costa E.Perren G.Moitinho A.2017-06-21T08:22:49Z2012-07-28T22:33:40ZCDS support team

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

cds-question@unistra.fropen-star-clustersvisible-astronomyWide-band photometryob-starsstellar-distancestellar-spectral-typesearly-type-starsIn this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20kpc. These groups are located in the area of two cataloged open clusters (VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color-color and color-magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance (~20kpc) where no young stars have been detected so far in the optical.2010ApJ...718..683Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/718/683CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2012)II/183 : UBVRI Photometric Standards (Landolt 1992)J/A+A/511/A38 : Open clusters in third galactic quadrant (Vazquez+, 2010)J/ApJ/672/930 : Distant CO clouds in third galactic quadrant (Vazquez+, 2008)J/A+A/464/573 : VI photometry of 5 open clusters (Carraro+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/718/683https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/718/683http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/718/683https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/718/683https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/718/683http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/718/683GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/718/683/table3 (Basic properties of the early spectral-type stars encountered in Field 1 (VdB-Hagen 04))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/718/683/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/718/683/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/718/683/table3?GETtext/xml+votable180.050000true114.43157-36.146460.005555555555555556Cone search capability for table J/ApJ/718/683/table4 (Basic properties of the early spectral-type stars encountered in Field 2 (Ruprecht 30))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/718/683/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/718/683/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/718/683/table4?GETtext/xml+votable180.050000true115.38756-31.391180.005555555555555556Cone search capability for table J/ApJ/718/683/vdbh4 (*List of (XY) positions for all VdB-Hagen 4 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/718/683/vdbh4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/718/683/vdbh4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/718/683/vdbh4?GETtext/xml+votable180.050000true114.2354028-35.89298190.005555555555555556Cone search capability for table J/ApJ/718/683/rup30 (*List of (XY) positions for all Ruprecht 30 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/718/683/rup30?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/718/683/rup30?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/718/683/rup30?GETtext/xml+votable180.050000true115.3428978-31.40108220.0055555555555555566/39704 39705 39776 39777 397793.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/718/683?format=asciiOpticaldefaultJ/ApJ/718/683/table3Basic properties of the early spectral-type stars encountered in Field 1 (VdB-Hagen 04)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[25/6107] Star identifiermeta.id;meta.mainintVmagV-band magnitudemagphot.mag;em.opt.VfloatB-VB-V color indexmagphot.color;em.opt.B;em.opt.VfloatU-BU-B color indexmagphot.color;em.opt.U;em.opt.BfloatE(B-V)B-V color excessmagphot.color.excessfloatE(B-V)0B-V color excess; corrected for extinctionmagphot.color.excessfloatE(U-B)0U-B color excess; corrected for extinctionmagphot.color.excessfloatVMagV-band absolute magnitudemagphot.mag;em.opt.VfloatSpTPhotometric MK spectral typesrc.spTypecharDistDistancekpcpos.distance;pos.heliocentricfloate_DistDist uncertaintykpcstat.errorfloat_RAPosition computed from CCD position (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from CCD position (declination part)degpos.eq.dec;meta.mainJ/ApJ/718/683/table4Basic properties of the early spectral-type stars encountered in Field 2 (Ruprecht 30)VmagV-band magnitudemagphot.mag;em.opt.VfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[25/6107] Star identifiermeta.id;meta.mainintB-VB-V color indexmagphot.color;em.opt.B;em.opt.VfloatU-BU-B color indexmagphot.color;em.opt.U;em.opt.BfloatE(B-V)B-V color excessmagphot.color.excessfloatE(B-V)0B-V color excess; corrected for extinctionmagphot.color.excessfloatE(U-B)0U-B color excess; corrected for extinctionmagphot.color.excessfloatVMagV-band absolute magnitudemagphot.mag;em.opt.VfloatSpTPhotometric MK spectral typesrc.spTypecharDistDistancekpcpos.distance;pos.heliocentricfloate_DistDist uncertaintykpcstat.errorfloat_RAPosition computed from CCD position (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from CCD position (declination part)degpos.eq.dec;meta.mainJ/ApJ/718/683/vdbh4*List of (XY) positions for all VdB-Hagen 4 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/3957] Star identifiermeta.id;meta.mainintXposCCD position along the X axispixpos.cartesian.x;instr.detdoubleYposCCD position along the Y axispixpos.cartesian.y;instr.detdoubleVmagV-band magnitudemagphot.mag;em.opt.VfloatB-V(B-V) colormagphot.color;em.opt.B;em.opt.VfloatU-B(U-B) colormagphot.color;em.opt.U;em.opt.BfloatID07? Identifier in Carraro et al. 2007, Cat. J/A+A/464/573meta.idintnullableWEBDAWEBDA ID (http://www.univie.ac.at/webda)meta.idint_RAPosition computed from a comparison with UCAC2 catalog I/289 ({sigma}=0.14'') (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from a comparison with UCAC2 catalog I/289 ({sigma}=0.14'') (declination part)degpos.eq.dec;meta.mainJ/ApJ/718/683/rup30*List of (XY) positions for all Ruprecht 30 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/6108] Star identifier, as in table3meta.id;meta.mainintVmagV-band magnitudemagphot.mag;em.opt.VfloatXposCCD position along the X axispixpos.cartesian.x;instr.detdoubleYposCCD position along the Y axispixpos.cartesian.y;instr.detdouble_RAPosition computed from a comparison with UCAC2 catalog I/289 ({sigma}=0.10'') (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from a comparison with UCAC2 catalog I/289 ({sigma}=0.10'') (declination part)degpos.eq.dec;meta.main