J/ApJ/420/612ivo://CDS.VizieR/J/ApJ/420/612doi:10.26093/cds/vizier.14200612CDSPeterson R.C.Cudworth K.M.2013-03-05T06:34:29Z1997-12-09T20:50:30ZCDS support team

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

cds-question@unistra.frglobular-star-clustersradial-velocitystellar-distanceThe distance to the globular cluster M22 is reexamined from new radial-velocity data and revised proper motions. Proper motions are rederived for 672 stars in the field of M22 using plate constant solutions from which stars of large proper motions have been removed, to reduce systematic errors which depend on coordinates. Radial velocities good to 1km/s have been obtained for 130 members of the globular cluster M22. The mean radial velocity is -148.8+/-0.8km/s. The radial velocity dispersion is 6.6+/-0.8km/s in the mean, and shows little if any dependence on distance from the cluster center over a 3'-7' annulus. Ignoring the small effect of rotation, a mass-to-light ratio M/L_V=0.85+/-0.15 in solar units is derived. The lack of stars moving faster than the escape velocity suggests strongly that a value M/L_V~1 applies to the cluster as a whole. This value is among the lowest observed for any globular cluster. Rotation is evident in both proper motions and radial velocities, and its position angle is in reasonable agreement with the major axis of the cluster's elongation. Its amplitude diminishes with radius, from ~6km/s for 1'<=r<= 3', to ~3km/s for 3'<=r<=7'. Rotation must be carefully modeled to determine an accurate distance to the cluster. From the simple approximation that the velocity dispersion is unaffected in the directions perpendicular to the streaming motion, a comparison of the dispersions in proper motion with those in radial velocity leads to a preliminary estimate for the distance of 2.6+/-0.3kpc, and a horizontal-branch magnitude M_V=0.71+/-0.27, using the reddening value E(B-V)=0.42 from M22 BHB stars.1994ApJ...420..612Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/420/612CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/420/612https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/420/612http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/420/612https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/420/612https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/420/612http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/420/612GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/420/612/table2 (Velocities for M22 members)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/420/612/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/420/612/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/420/612/table2?GETtext/xml+votable180.050000true279.0862732-23.92424790.005555555555555556Cone search capability for table J/ApJ/420/612/table3 (*Velocities for M22 field stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/420/612/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/420/612/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/420/612/table3?GETtext/xml+votable180.050000true279.0074268-23.95390490.0055555555555555566/28966 28967 28972 28973https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/420/612?format=asciiOpticaldefaultJ/ApJ/420/612/table2Velocities for M22 membersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2440000Julian date (-2440000) of each observationdtime.epochfloatRA1950Right ascension (equinox 1950.0)pos.eq.ra;meta.mainDE1950Declination (equinox 1950.0)pos.eq.dec;meta.mainDistRadial distance from cluster centerarcminphys.angSizefloatPAPosition angle positive north through eastdegpos.posAngfloatRVMeasured radial velocitykm/sphys.veloc;pos.heliocentricdoublee_RVInternal one-sigma uncertainty in RVkm/sstat.errorfloatVmagV magnitudemagphot.mag;em.opt.VfloatMembPercent probability of membership%statintIDIdentificationmeta.id;meta.mainchar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexedJ/ApJ/420/612/table3*Velocities for M22 field starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2440000Julian date (-2440000) of each observationdtime.epochfloatRA1950Right ascension (equinox 1950.0)pos.eq.ra;meta.mainDE1950Declination (equinox 1950.0)pos.eq.dec;meta.mainDistRadial distance from cluster centerarcminphys.angSizefloatPAPosition angle positive north through eastdegpos.posAngfloatRVMeasured radial velocitykm/sphys.veloc;pos.heliocentricdoublee_RVInternal one-sigma uncertainty in RVkm/sstat.errorfloatVmagV magnitudemagphot.mag;em.opt.VfloatMembPercent probability of membership%statintIDIdentificationmeta.id;meta.mainchar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexedJ/ApJ/420/612/table4Stars with multiple velocity measurementsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2440000Julian date (-2440000) of each observationdtime.epochdoubleRVMeasured radial velocitykm/sphys.veloc;pos.heliocentricdoublee_RVInternal uncertainty in RVkm/sstat.errorfloatVmag[]? V magnitudemagphot.mag;em.opt.VfloatnullableIDIdentificationmeta.id;meta.mainchar