J/AJ/148/27ivo://CDS.VizieR/J/AJ/148/27doi:10.26093/cds/vizier.51480027CDSCummings J.D.Geisler D.Villanova S.Carraro G.2014-11-01T14:46:37Z2014-10-15T09:56:04ZCDS support team

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

cds-question@unistra.frglobular-star-clustersvisible-astronomybroad-band-photometryThe analysis of multiple populations (MPs) in globular clusters (GCs) has become a forefront area of research in astronomy. Multiple red giant branches (RGBs), subgiant branches (SGBs), and even main sequences (MSs) have now been observed photometrically in many GCs, while broad abundance distributions of certain elements have been detected spectroscopically in most, if not all, GCs. UV photometry has been crucial in discovering and analyzing these MPs, but the Johnson U and the Stromgren and Sloan u filters that have generally been used are relatively inefficient and very sensitive to reddening and atmospheric extinction. In contrast, the Washington C filter is much broader and redder than these competing UV filters, making it far more efficient at detecting MPs and much less sensitive to reddening and extinction. Here, we investigate the use of the Washington system to uncover MPs using only a 1 m telescope. Our analysis of the well-studied GC NGC 1851 finds that the C filter is both very efficient and effective at detecting its previously discovered MPs in the RGB and SGB. Remarkably, we have also detected an intrinsically broad MS best characterized by two distinct but heavily overlapping populations that cannot be explained by binaries, field stars, or photometric errors. The MS distribution is in very good agreement with that seen on the RGB, with ~30% of the stars belonging to the second population. There is also evidence for two sequences in the red horizontal branch, but this appears to be unrelated to the MPs in this cluster. Neither of these latter phenomena have been observed previously in this cluster. The redder MS stars are also more centrally concentrated than the blue MS. This is the first time MPs in an MS have been discovered from the ground, and using only a 1 m telescope. The Washington system thus proves to be a very powerful tool for investigating MPs, and holds particular promise for extragalactic objects where photons are limited.2014AJ....148...27Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/148/27CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/202 : Globular Clusters in the Milky Way (Harris, 1997)J/A+A/539/A19 : Horizontal branch stars in NGC 1851 (Gratton+, 2012)J/A+A/533/A69 : Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)J/AJ/122/2569 : VI photometry of NGC 288, 362 and 1851 (Bellazzini+, 2001)J/PASP/104/1063 : BV Color-Magnitude Diagram for NGC 1851 (Walker 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/148/27https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/148/27http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/148/27https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/148/27https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/148/27http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/148/27GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/148/27/table2 (The Washington photometric catalog of NGC 1851)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/148/27/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/148/27/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/148/27/table2?GETtext/xml+votable180.050000true78.5734756-39.82240970.0055555555555555566/34242 342432.285239626323992e-19 5.696014567210867e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/148/27?format=asciiOpticaldefaultJ/AJ/148/27/table2The Washington photometric catalog of NGC 1851o_Cmag[0/11] Number of independent observations for Cmagmeta.numberintName[2/18461] Source identifier \dicS{[CGV2014] NNNNN} in Simbadmeta.id;meta.mainintprimaryXposX pixel coordinate (scale=0.435arcsec/pix)pixpos.cartesian.xfloatYposY pixel coordinate (scale=0.435arcsec/pix)pixpos.cartesian.yfloatCmag? Final Washington C band magnitudemagphot.mag;em.opt.Ufloatnullablee_Cmag? Error in Cmagmagstat.error;phot.magfloatnullables_Cmag? Photometric dispersion in Cmagmagstat.variancefloatnullableT1magFinal Washington T1 band magnitudemagphot.mag;em.opt.Rfloate_T1magError in T1magmagstat.error;phot.magfloato_T1mag[1/4] Number of independent observations for T1magmeta.numberints_T1mag? Photometric dispersion in T2magmagstat.variancefloatnullableT2mag? Final Washington T2 band magnitudemagphot.mag;em.opt.Ifloatnullablee_T2mag? Error in T2magmagstat.error;phot.magfloatnullableo_T2mag[0/4] Number of independent observations for T2magmeta.numberints_T2mag? Photometric dispersion in T2magmagstat.variancefloatnullable_RAPosition computed from a comparison with DENIS catalog (B/denis) ({sigma}=0.14'') (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from a comparison with DENIS catalog (B/denis) ({sigma}=0.14'') (declination part)degpos.eq.dec;meta.main