J/MNRAS/439/788ivo://CDS.VizieR/J/MNRAS/439/788doi:10.26093/cds/vizier.74390788CDSHughes J.Wallerstein G.Dotter A.Geisler D.2024-08-08T20:12:56Z2015-03-09T09:08:50ZCDS support team

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

cds-question@unistra.frgalaxiesvisible-astronomybroad-band-photometryinfrared-photometryWe present new Stromgren and Washington data sets for the Bootes I dwarf galaxy, and combine them with the available Sloan Digital Sky Survey photometry. The goal of this project is to refine a ground-based, practical, accurate method to determine age and metallicity for individual stars in Bootes I that can be selected in an unbiased imaging survey, without having to take spectra. With few bright upper red giant branch stars and distances of about 35-250kpc, the ultra-faint dwarf galaxies (UDFs) present observational challenges in characterizing their stellar population. Other recent studies have produced spectra and proper motions, making Bootes I an ideal test case for our photometric methods. We produce photometric metallicities from Stromgren and Washington photometry, for stellar systems with a range of -1.0>[Fe/H]>-3.5. Needing to avoid the collapse of the metallicity sensitivity of the Stromgren m1-index on the lower red giant branch, we replace the Stromgren v filter with the broader Washington C filter to minimize observing time. We construct two indices: m*=(C-T1)0-(T1-T2)0 and m**=(C-b)0-(b-y)0. We find that CT1by is the most successful filter combination, for individual stars with [Fe/H] < -2.0, to maintain ~0.2dex [Fe/H]-resolution over the whole red giant branch. The m**-index would be the best choice for space-based observations because the (C-y) colour is not sufficient to fix metallicity alone in an understudied system. Our photometric metallicites of stars in the central regions of Bootes I confirm that there is a metallicity spread of at least -1.9>[Fe/H]>-3.7. The best-fitting Dartmouth isochrones give a mean age, for all the Bootes I stars in our data set, of 11.5+/-0.4Gyr. From ground-based telescopes, we show that the optimal filter combination is CT1by, avoiding the v filter entirely. We demonstrate that we can break the isochrones' age-metallicity degeneracy with the CT1by filters, using stars with logg=2.5-3.0, which have less than a 2percent change in their (C-T1) colour due to age, over a range of 10^-14^Gyr.2014MNRAS.439..788Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/439/788CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/136/2321 : Washington photometry of Bootes I stars (Hughes+, 2008)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/439/788https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/439/788http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/439/788https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/439/788https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/439/788http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/439/788GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/439/788/table3 (Objects in Bootes I with Washington and Stroemgren photometry)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/439/788/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/439/788/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/439/788/table3?GETtext/xml+votable180.050000true209.640916714.35236110.0055555555555555566/8744-87452.9196443747461696e-19 3.2860540898823595e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/439/788?format=asciiOpticalInfrareddefaultJ/MNRAS/439/788/table3Objects in Bootes I with Washington and Stroemgren photometrySimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCode[1/3] Code (1)meta.codeintHWB[2/163]? Hughes et al. name (see J/AJ/136/2321) <[HWB2008] NNN> in Simbadmeta.id;meta.mainintnullableBooI? Other name, <[NWG2010] BooI NNNN> in Simbadmeta.idintnullableXpos? X position from the Fig. 1pixpos.cartesian.x;instr.detfloatnullableYpos? Y position from the Fig. 1pixpos.cartesian.y;instr.detfloatnullableRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainMm[A-F] HWB's photometric membership class (2)meta.notecharT1mag[14/24] Washington T1 magnitudemagphot.mag;em.opt.Rfloate_T1mag[0.01/0.12] rms uncertainty on T1magmagstat.error;phot.magfloatC-T1Washington C-T1 colour indexmagphot.color;em.opt.U;em.opt.Rfloate_C-T1rms uncertainty on C-T1magstat.errorfloatT1-T2Washington T1-T2 colour indexmagphot.color;em.opt.R;em.opt.Ifloate_T1-T2rms uncertainty on T1-T2magstat.errorfloatVmag[14/24.7] Stroemgren V magnitudemagphot.mag;em.opt.Bfloate_Vmagrms uncertainty on Vmagmagstat.error;phot.mag;em.opt.Vfloatb-yStroemgren b-y colour indexmagphot.color;em.opt.B;em.opt.Vfloate_b-yrms uncertainty on b-ymagstat.error;phot.color;em.opt.Bfloatm1? Stroemgren m1 indexmagphot.colorfloatnullablee_m1? rms uncertainty on m1magstat.errorfloatnullable