J/ApJS/247/7ivo://CDS.VizieR/J/ApJS/247/7doi:10.26093/cds/vizier.22470007CDSHan S.-I.Kim H.-S.Yoon S.-J.Lee Y.-W.Arimoto N.Okamoto S.,Ree C.H.2021-09-06T19:12:15Z2020-06-18T15:39:48ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryvisible-astronomyA few dozen dwarf satellite galaxies of the Milky Way have been discovered, which are often viewed as the remaining building blocks of our Galaxy. The follow-up spectroscopy showed that dwarf galaxies have a sizeable spread in their metallicities. Several scenarios were suggested to explain the metallicity spread, which can be tested by the structural patterns of stellar subpopulations with distinct metallicities. However, such chemical plus structural examination, which we refer to as "chemostructural study", is hindered by the lack of stars with spectroscopic metallicity. Here we propose the Ca-by photometry as an alternative way to secure metallicities for a 2-3 orders of magnitude larger stellar sample than the spectroscopic sample and thus enable us to perform a chemostructural study on dwarf galaxies. In particular, we use the hk index [=(Ca-b)-(b-y)], whose validity as a photometric metallicity indicator (and crass insensitivity to age) for red-giant-branch stars was upheld via Galactic globular clusters, and observe three dwarf spheroidal galaxies-Draco, Sextans, and Canes Venatici I (CVnI)-with Subaru/Suprime-Cam. We find that in all the galaxies the metal-rich stellar populations are more centrally concentrated than the metal-poor counterparts, suggesting that the central regions of the galaxies underwent extended star formation. Such a negative radial metallicity gradient for Sextans and CVnI opposes the traditional spectroscopic results. We also find that their metallicity distribution functions (MDFs) can be characterized by a unimodal, skewed Gaussian shape with a metal-rich peak and a metal-poor tail.2020ApJS..247....7Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/247/7CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/284 : The USNO-B1.0 Catalog (Monet+ 2003)J/PASP/107/32 : uvby-hk photometry in M22 (Anthony-Twarog+ 1995)J/AJ/116/1922 : CaII H and K filter photometry III. (Anthony-Twarog+, 1998)J/AJ/119/1824 : Caby photometry of {Omega} Centauri (Rey+, 2000)J/AJ/125/1383 : Stromgren photometry of NGC 6253 (Anthony-Twarog+, 2003)J/AJ/127/1000 : Stromgren & Ca photom. of NGC 3680 (Anthony-Twarog+, 2004)J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)J/A+A/454/333 : Computed Hbeta indices from ATLAS9 model (Castelli+, 2006)J/AJ/131/895 : Stars in the Carina dwarf spheroidal galaxy (Koch+, 2006)J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)J/AJ/142/127 : NGC 5822 UBVI and uvbyCaH{beta} photometry (Carraro+, 2011)J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)J/ApJ/778/L13 : Subaru new Ca filter transmission function (Lee+, 2013)J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)J/ApJS/216/19 : Spectroscopic HK' index for 3 globular clusters (Lim+, 2015)J/MNRAS/456/3757 : Open-cluster density profiles (Seleznev, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/247/7https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/247/7http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/247/7https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/247/7https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/247/7http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/247/7GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/247/7/table2 (Photometric measurements for the point sources in Draco)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/247/7/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/247/7/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/247/7/table2?GETtext/xml+votable180.050000true260.4898638957.781853060.005555555555555556Cone search capability for table J/ApJS/247/7/table3 (Photometric measurements for the point sources in Sextans)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/247/7/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/247/7/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/247/7/table3?GETtext/xml+votable180.050000true153.41356306-1.701420.005555555555555556Cone search capability for table J/ApJS/247/7/table4 (Photometric measurements for the point sources in Canes Venatici I (CVnI))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/247/7/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/247/7/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/247/7/table4?GETtext/xml+votable180.050000true202.1536919433.686321110.0055555555555555566/10181 10182 10183 10441 10443 10444 10446 27207 27218https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/247/7?format=asciiOpticaldefaultJ/ApJS/247/7/table2Photometric measurements for the point sources in DracoSHARP[-5.51/11.2] DAOPHOT SHARP parameterstat.paramfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainindexedCa[14.1/28.1] The Subaru/Sprime-Cam Ca narrow filter magnitude (1)magphot.mag;em.optfloate_Ca[0.001/1.6] Uncertainty in Camagstat.errorfloatb[12.5/27.7] The Subaru/Sprime-Cam b narrow filter magnitude (1)magphot.mag;em.optfloate_b[0.001/1.6] Uncertainty in bmagstat.errorfloaty[12.3/27.4] The Subaru/Sprime-Cam y narrow filter magnitude (1)magphot.mag;em.optfloate_y[0.001/1.7] Uncertainty in ymagstat.error;pos.cartesian.yfloatCHI[0.2/23.2] DAOPHOT CHI parameterstat.fit.chi2floatJ/ApJS/247/7/table3Photometric measurements for the point sources in SextansrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainindexedCa[14.1/28.1] The Subaru/Sprime-Cam Ca narrow filter magnitude (1)magphot.mag;em.optfloate_Ca[0.001/1.6] Uncertainty in Camagstat.errorfloatb[12.5/27.7] The Subaru/Sprime-Cam b narrow filter magnitude (1)magphot.mag;em.optfloate_b[0.001/1.6] Uncertainty in bmagstat.errorfloaty[12.3/27.4] The Subaru/Sprime-Cam y narrow filter magnitude (1)magphot.mag;em.optfloate_y[0.001/1.7] Uncertainty in ymagstat.error;pos.cartesian.yfloatCHI[0.2/23.2] DAOPHOT CHI parameterstat.fit.chi2floatSHARP[-5.51/11.2] DAOPHOT SHARP parameterstat.paramfloatJ/ApJS/247/7/table4Photometric measurements for the point sources in Canes Venatici I (CVnI)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainindexedCa[14.1/28.1] The Subaru/Sprime-Cam Ca narrow filter magnitude (1)magphot.mag;em.optfloate_Ca[0.001/1.6] Uncertainty in Camagstat.errorfloatb[12.5/27.7] The Subaru/Sprime-Cam b narrow filter magnitude (1)magphot.mag;em.optfloate_b[0.001/1.6] Uncertainty in bmagstat.errorfloaty[12.3/27.4] The Subaru/Sprime-Cam y narrow filter magnitude (1)magphot.mag;em.optfloate_y[0.001/1.7] Uncertainty in ymagstat.error;pos.cartesian.yfloatCHI[0.2/23.2] DAOPHOT CHI parameterstat.fit.chi2floatSHARP[-5.51/11.2] DAOPHOT SHARP parameterstat.paramfloat