J/ApJ/720/1055ivo://CDS.VizieR/J/ApJ/720/1055doi:10.26093/cds/vizier.17201055CDSSato M.Reid M.J.Brunthaler A.Menten K.M.2018-02-02T10:34:12Z2012-08-22T12:05:01ZCDS support team

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

cds-question@unistra.frastrophysical-masersradio-astronomyproper-motionsh-ii-regionsvery-long-baseline-interferometryWe report measurement of the trigonometric parallax of W51 Main/South using the Very Long Baseline Array. We measure a value of 0.185+/-0.010mas corresponding to a distance of 5.41^+0.31^_-0.28_kpc. W51 Main/South is a well-known massive star-forming region near the tangent point of the Sagittarius spiral arm of the Milky Way. Our distance to W51 yields an estimate of the distance to the Galactic center of R_0_=8.3+/-0.46(statistical)+/-1.0(systematic)kpc by simple geometry. Combining the parallax and proper motion measurements for W51, we obtained the full-space motion of this massive star-forming region. We find W51 is in a nearly circular orbit about the Galactic center. The H_2_O masers used for our parallax measurements trace four powerful bipolar outflows within a 0.4pc size region, some of which are associated with dusty molecular hot cores and/or hyper- or ultra-compact HII regions.2010ApJ...720.1055Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/720/1055CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJS/191/232 : CO survey of W51 molecular cloud (Bieging+, 2010)J/ApJ/706/83 : Embedded YSO candidates in W51 (Kang+, 2009)J/A+A/473/177 : A search for pre-biotic molecules (Wirstrom+, 2007)J/MNRAS/353/1025 : JHK photometry of 4 W51 star clusters (Nanda+, 2004)J/A+A/368/845 : Arcetri Catalog of H2O maser sources. Update. (Valdettaro+,J/A+A/358/257 : Molecular clouds SO and CS obs. II. (Nilsson+, 2000)J/ApJ/463/205 : CS and NH3 Survey of H2O Maser Emission (Anglada+ 1996)J/A+AS/101/153 : Galactic H2O masers (Palagi+ 1993)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/720/1055https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/720/1055http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/720/1055https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/720/1055https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/720/1055http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/720/1055GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/720/1055/table3H_2_O maser feature motions in W51 Main/SouthrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRegRegion identification (1)meta.id;obs.fieldcharID[1/37] Maser feature numbermeta.number;phys.atmol.number;meta.mainintprimaryVlsrLSR velocitykm/sphys.veloc;pos.lsrfloatTbBrightness temperature in units of Jy/beam (2)Jyphot.flux.density;arith.ratiofloatx0X position relative to feature 32 (3)arcsecpos.cartesian.x;pos.galactocentricfloate_x0Uncertainty in x0arcsecstat.errorfloaty0Y position relative to feature 32 (3)arcsecpos.cartesian.y;pos.galactocentricfloate_y0Uncertainty in y0arcsecstat.errorfloatpmxProper motion along X (4)mas/yrpos.pm;pos.cartesian.xfloate_pmxUncertainty in pmxmas/yrstat.errorfloatpmyProper motion along Y (4)mas/yrpos.pm;pos.cartesian.yfloate_pmyUncertainty in pmymas/yrstat.errorfloatJ/ApJ/720/1055/table4Maser spot motions in W51 Main/SouthrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/37] Maser spot IDs in different velocity channels in each feature (as in table 3)phys.veloc;meta.mainintprimaryNum[1/7] IDs of the component spots in different velocity channels for each featurepos.cartesianintVlsrLocal Standard of Rest Velocitykm/sphys.veloc;pos.lsrfloatTbBrightness temperature in units of Jy/beamJyphot.flux.density;arith.ratiofloatx0X position relative to feature 32 spot number 3arcsecpos.cartesian.x;pos.galactocentricfloate_x0Uncertainty in x0arcsecstat.errorfloaty0Y position relative to feature 32 spot number 3arcsecpos.cartesian.y;pos.galactocentricfloate_y0Uncertainty in y0arcsecstat.errorfloatpmxProper motion along Xmas/yrpos.pm;pos.cartesian.xfloate_pmxUncertainty in pmxmas/yrstat.errorfloatpmyProper motion along Ymas/yrpos.pm;pos.cartesian.yfloate_pmyUncertainty in pmymas/yrstat.errorfloat