J/A+A/547/A15ivo://CDS.VizieR/J/A+A/547/A15doi:10.26093/cds/vizier.35470015CDSNegueruela I.Marco A.Gonzalez-Fernandez C.Jimenez-Esteban F.,Clark J.S.Garcia M.Solano E.2017-07-06T06:25:46Z2013-03-11T13:20:39ZCDS support team

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

cds-question@unistra.fropen-star-clustersgiant-starsinfrared-photometryradial-velocitySeveral clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red supergiants, is a strong candidate to be the most massive young cluster in the Galaxy. Stephenson 2 is located close to a region where a strong over-density of red supergiants had been found. We explore the actual cluster size and its possible connection to this over-density. Taking advantage of Virtual Observatory tools, we have performed a cross-match between the DENIS, USNO-B1 and 2MASS catalogues to identify candidate obscured luminous red stars around Stephenson 2, and in a control nearby region. More than 600 infrared bright stars fulfill our colour criteria, with the vast majority having a counterpart in the I band and >400 being sufficiently bright in I to allow observation with a 4-m class telescope. We observed a subsample of ~250 stars, using the multi-object, wide-field, fibre spectrograph AF2 on the WHT telescope in La Palma, obtaining intermediate-resolution spectroscopy in the 7500-9000{AA} range. We derived spectral types and luminosity classes for all these objects and measured their radial velocities.2012A&A...547A..15Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/547/A15CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/denis : The DENIS database (DENIS Consortium, 2005)I/284 : The USNO-B1.0 Catalog (Monet+ 2003)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)J/ApJ/671/781 : Red supergiants in Sct-Cru Galactic arm (Davies+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/547/A15https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/547/A15http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/547/A15https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/547/A15https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/547/A15http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/547/A15GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/547/A15/stars (Photometry and spectroscopy of the observed targets)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/547/A15/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/547/A15/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/547/A15/stars?GETtext/xml+votable180.050000true279.583875-5.72872220.0055555555555555566/30218-30219 30222-30223 30234 30241 30244-30245 302567.952274030004205e-20 1.7798557115773645e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/547/A15?format=asciiOpticalInfrareddefaultJ/A+A/547/A15/starsPhotometry and spectroscopy of the observed targetsn_2MASS[a+] Note (1)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInsSimbad column added by the CDSmeta.id;instrchar2MASS2MASS name (HHMMSSss+DDMMSSs)meta.id;meta.maincharDFK[1/39]? ID in Davies et al. 2007ApJ...671..781D <Cl* Stephenson 2 DFK NN> in Simbadmeta.idintnullableJmagJ magnitudemagphot.mag;em.IR.Jfloate_Jmagrms uncertainty on Jmagmagstat.error;phot.mag;em.IR.JfloatHmagH magnitudemagphot.mag;em.IR.Hfloate_Hmag? rms uncertainty on Hmagmagstat.error;phot.mag;em.IR.Hfloatnullablel_Hmag[c] c: Hmag is an upper limitmeta.code.errorcharKsmagKs magnitudemagphot.mag;em.IR.Kfloate_Ksmagrms uncertainty on Ksmagmagstat.error;phot.mag;em.IR.Kfloatl_E(J-Ks)Limit flag on E(J-Ks)meta.code.errorcharE(J-Ks)J-Ks colour excessmagphot.color.excessfloatVlsrLocal Standard of Rest velocitykm/sphys.veloc;pos.lsrintSpTypeMK spectral typesrc.spTypecharn_SpType[b] b: blended source (see Sect. 4)meta.notecharSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPosition from 2MASS name (right ascension part)degpos.eq.ra;meta.main_DEPosition from 2MASS name (declination part)degpos.eq.dec;meta.main