J/ApJ/818/39ivo://CDS.VizieR/J/ApJ/818/39doi:10.26093/cds/vizier.18180039CDSHargis J.R.Kimmig B.Willman B.Caldwell N.Walker M.G.Strader J.,Sand D.J.Grillmair C.J.Yoon J.H.2018-09-13T08:44:44Z2016-05-24T11:38:00ZCDS support team

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

cds-question@unistra.frradial-velocitychemical-abundancesinfrared-photometryvisible-astronomybroad-band-photometryThe Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d~10kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (~5-6Gyr) and metallicity ([Fe/H]=-0.9dex). We measure statistically significant spreads in both the iron and alpha-element abundances of {sigma}_[Fe/H]_=0.13+/-0.02dex and {sigma}_[{alpha}/Fe]_=0.09+/-0.03dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H] --as well as its low [{alpha}/Fe], apparent [Fe/H] spread, and present-day low luminosity-- suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.2016ApJ...818...39Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/818/39CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/448/2717 : Resolved stellar spectra Bayesian analysis (Walker+, 2015)J/AJ/149/53 : RVs of 12 Milky Way globular clusters (Kimmig+, 2015)J/MNRAS/446/730 : VIJK photometry of Whiting 1 stars (Valcheva+, 2015)J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)J/ApJ/754/101 : Monoceros Overdensity deep imaging with Subaru (Conn+, 2012)J/AJ/144/4 : Local Group dwarf galaxy properties (McConnachie+, 2012)J/AJ/141/90 : SEGUE stellar parameter pipeline. V. (Lee+, 2011)J/AJ/141/61 : Star clusters in M31. II. (Caldwell+, 2011)J/ApJ/703/2177 : Metal-poor MS turnoff stars summary (Schlaufman+, 2009)J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)J/A+A/486/697 : Hydra I Cluster Catalogue (HCC) (Misgeld+, 2008)J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)J/ApJS/85/249 : Surface Photometry of Hydra I Galaxies. I. (Hamabe 1993)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/818/39https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/818/39http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/818/39https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/818/39https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/818/39http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/818/39GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/818/39/table1 (DECam photometry)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/818/39/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/818/39/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/818/39/table1?GETtext/xml+votable180.050000true132.348948893.153806110.005555555555555556Cone search capability for table J/ApJ/818/39/table2 (Hectochelle/MMT spectroscopy)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/818/39/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/818/39/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/818/39/table2?GETtext/xml+votable180.050000true134.208388893.950311940.005555555555555556Cone search capability for table J/ApJ/818/39/table3 (SDSS/SEGUE spectroscopy)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/818/39/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/818/39/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/818/39/table3?GETtext/xml+votable180.050000true132.57293.247481110.0055555555555555565/1026 1027 6/4098 4099 4102 4103 4122 4128 4129 4132 4133 4134 4144https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/818/39?format=asciiInfraredOpticaldefaultJ/ApJ/818/39/table1DECam photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000) (1)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000) (1)degpos.eq.dec;meta.mainindexedgmag[16.1/24.2] Calibrated g band magnitude (2)magphot.mag;em.opt.Bfloate_gmag[0/0.6] The 1{sigma} uncertainty in gmagmagstat.error;phot.mag;em.opt.Bfloatrmag[16.5/24] Calibrated r band magnitude (2)magphot.mag;em.opt.Rfloate_rmag[0.001/0.4] The 1{sigma} uncertainty in rmagmagstat.error;phot.mag;em.opt.RfloatE(B-V)[0.02/0.07] The (B-V) color excessmagphot.color.excessfloatJ/ApJ/818/39/table2Hectochelle/MMT spectroscopyrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000) (1)degpos.eq.dec;meta.mainHRV[-98/293] Heliocentric radial velocity (2)km/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[0.3/2.1] The 1{sigma} uncertainty in HRV (2)km/sstat.errorfloatgmag[17/21.13] Calibrated g band magnitude (G1)magphot.mag;em.opt.Bfloate_gmag[0.003/0.02] The 1{sigma} uncertainty in gmagmagstat.error;phot.mag;em.opt.Bfloatrmag[16.51/20.76] Calibrated r band magnitude (G1)magphot.mag;em.opt.Rfloate_rmag[0.002/0.02] The 1{sigma} uncertainty in rmagmagstat.error;phot.mag;em.opt.RfloatE(B-V)[0.03/0.06] The (B-V) color excessmagphot.color.excessfloatSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/818/39/table3SDSS/SEGUE spectroscopySimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000) (1)degpos.eq.dec;meta.mainHRV[-147/299] Heliocentric radial velocity (2)km/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[0.4/15] The 1{sigma} uncertainty in HRVkm/sstat.errorfloat[Fe/H][-2.9/0.2] Log Fe/H abundance ratio (2)phys.abund.Fe;arith.ratiofloate_[Fe/H][0.001/0.3] The 1{sigma} uncertainty in [Fe/H]stat.error;phys.abund.Fefloat[a/Fe][-0.05/0.6] Log {alpha}/Fe abundance ratio (2)phys.abundfloate_[a/Fe][0.002/0.05] The 1{sigma} uncertainty in [a/Fe]stat.error;phys.abundfloatgmag[15.56/20.5] Calibrated g band magnitude (G1)magphot.mag;em.opt.Bfloate_gmag[0.003/0.02] The 1{sigma} uncertainty in gmagmagstat.error;phot.mag;em.opt.Bfloatrmag[14.98/20.1] Calibrated r band magnitude (G1)magphot.mag;em.opt.Rfloate_rmag[0.002/0.04] The 1{sigma} uncertainty in rmagmagstat.error;phot.mag;em.opt.RfloatE(B-V)[0.02/0.06] The (B-V) color excessmagphot.color.excessfloatSloanDisplay the SDSS data for the nearest objectmeta.ref.urlchar