J/ApJS/219/7ivo://CDS.VizieR/J/ApJS/219/7doi:10.26093/cds/vizier.22190007CDSLee J.-W.2015-10-14T11:24:58Z2015-09-21T15:22:02ZCDS support team

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

cds-question@unistra.frglobular-star-clustersvisible-astronomymedium-band-photometrygiant-starsWe investigate the multiple stellar populations in one of the peculiar globular clusters (GCs), M22, using new ground-based wide-field Ca by and Hubble Space Telescope Wide-Field Camera 3 photometry with equivalent passbands, confirming our previous result that M22 has a distinctive red giant branch (RGB) split mainly due to the difference in metal abundances. We also make use of radial velocity measurements by others of the large number of cluster membership stars. Our main results are the following. (1) The RGB and the subgiant branch number ratios show that the calcium-weak (Ca-w) group is the dominant population of the cluster. However, an irreconcilable difference can be seen in the rather simple classification into two horizontal branches by others. (2) Each group has its own CN-CH anticorrelation. However, the alleged CN-CH positive correlation is likely illusory. (3) The location of the RGB bump of the calcium-strong (Ca-s) group is significantly fainter, which may pose a challenge to the helium enhancement scenario in the Ca-s group. (4) The positions of the centers are similar. (5) The Ca-w group is slightly more centrally concentrated, whereas the Ca-s is more elongated at larger radii. (6) The mean radial velocities for both groups are similar, but the Ca-s group has a larger velocity dispersion. (7) The Ca-s group rotates faster. The plausible scenario for the formation of M22 is that it formed via a merger of two GCs in a dwarf galaxy environment and accreted later to our Galaxy.2015ApJS..219....7Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/219/7CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)VII/202 : Globular Clusters in the Milky Way (Harris, 1997)J/ApJ/804/71 : HST/WFC3 observations of stars in M15 (Larsen+, 2015)J/ApJS/216/19 : Spectroscopic HK' index for 3 globular clusters (Lim+, 2015)J/MNRAS/442/3044 : Photometry and abundances of NGC1851 stars (Marino+, 2014)J/A+A/563/A80 : Wide field imagers ground-based astrometry (Libralato+, 2014)J/A+A/563/A76 : CaII triplet equivalent widths in 30 globulars (Mauro+, 2014)J/A+A/563/A13 : Horizontal branch stars in M22 (Gratton+, 2014)J/MNRAS/437/1609 : NGC 2808 HB stars abundances (Marino+, 2014)J/ApJ/778/L13 : Subaru new Ca filter transmission function (Lee+, 2013)J/MNRAS/431/1995 : Deep uVI photometry of NGC2419 (Beccari+, 2013)J/A+A/541/A15 : Abundances of M22 subgiants (Marino+, 2012)J/A+A/540/A27 : Spectroscopy in Galactic globular clusters (Saviane+, 2012)J/ApJ/742/37 : Abundances of six RGB stars in M22 (Roederer+, 2011)J/AJ/142/126 : CN & CH in SDSS Galactic globular clusters (Smolinski+, 2011)J/A+A/533/A69 : Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)J/A+A/526/A136 : Hot HB stars in {omega} Cen (Moehler+, 2011)J/A+A/524/A44 : CN and CH line strengths in 12 globulars (Pancino+, 2010)J/ApJ/705/1481 : Spectroscopy of stars in 6 globular clusters (Da Costa+, 2009)J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)J/A+A/486/437 : CN and CH line strengths in 8 Galactic GlCl (Kayser+, 2008)J/ApJ/654/915 : Deep FORS1 BR photometry of omega Cen (Sollima+, 2007)J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)J/MNRAS/349/1278 : BVI photometry of M22 (Monaco+, 2004)J/AJ/125/197 : CN abundances of the 47 Tuc main sequence (Harbeck+, 2003)J/A+A/373/899 : New variables in M22 globular cluster (Kaluzny+, 2001)J/AJ/116/1922 : CaII H and K filter photometry III. (Anthony-Twarog+, 1998)J/AJ/109/2828 : CaII H and K filter photometry II. (Twarog+ 1995)J/PASP/107/32 : uvby-hk photometry in M22 (Anthony-Twarog+ 1995)J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)J/ApJS/99/637 : Equivalent widths for 54 red giants (Norris+ 1995)J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/219/7https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/219/7http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/219/7https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/219/7https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/219/7http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/219/7GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/219/7/table3 (Color-magnitude diagram data)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/219/7/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/219/7/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/219/7/table3?GETtext/xml+votable180.050000true279.50201389-24.0073050.0055555555555555566/28966 28967 28972 289733.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/219/7?format=asciiOpticaldefaultJ/ApJS/219/7/table3Color-magnitude diagram datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/591556] Stellar identifiermeta.id;meta.mainintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainindexedVmag[8.6/19] The V band magnitudemagphot.mag;em.opt.Vfloatb-y[-4.7/8.3]? The Stromgren (b-y) color indexmagphot.color;em.opt.B;em.opt.Vfloatnullablehk[-11.4/13.6]? The hk index (1)magspect.indexfloatnullable