J/ApJ/834/9ivo://CDS.VizieR/J/ApJ/834/9doi:10.26093/cds/vizier.18340009CDSKirby E.N.Rizzi L.Held E.V.Cohen J.G.Cole A.A.Manning E.M.,Skillman E.D.Weisz D.R.2020-07-01T09:56:03Z2017-06-15T12:31:07ZCDS support team

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

cds-question@unistra.frchemical-abundancesradial-velocitygalaxiesspectroscopyinfrared-photometryvisible-astronomyphotometryWe present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies-but especially Leo A and Aquarius-share in common delayed star formation histories (SFHs) relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating HI gas. The velocity dispersions indicate that all three galaxies are dark-matter-dominated, with dark-to-baryonic mass ratios ranging from 4.4_-0.8_^+1.0^ (SagDIG) to 9.6_-1.8_^+2.5^ (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were further along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a closed or leaky box model of chemical evolution, suggesting that the galaxy was pre-enriched or acquired external gas during star formation. The metallicities of stars increased steadily for all three galaxies, but possibly at different rates. The [{alpha}/Fe] ratios at a given [Fe/H] are lower than that of the Sculptor dwarf spheroidal galaxy, which indicates more extended SFHs than Sculptor, consistent with photometrically derived SFHs. Overall, the bulk kinematic and chemical properties for the late-forming dwarf galaxies do not diverge significantly from those of less delayed dwarf galaxies, including dwarf spheroidal galaxies.2017ApJ...834....9Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/834/9CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/455/2163 : BI LCs of DDO210 pulsating variables (Ordonez+, 2016)J/ApJS/216/10 : DUSTiNGS. I. The Good Source Catalog (Boyer+, 2015)J/ApJ/801/125 : Carbon in red giants in GCs and dSph galaxies (Kirby+, 2015)J/ApJ/798/77 : Metallicity of RGB stars in 6 M31 dwarf galaxies (Ho+, 2015)J/A+A/572/A42 : SagDIG carbon and oxygen stars (Momany+, 2014)J/ApJS/214/19 : Suprime-Cam wide-field photometry of Leo A (Stonkute+, 2014)J/A+A/570/A78 : Deep VI photometry of Sgr dIrr (Beccari+, 2014)J/ApJ/790/73 : RGB iron & alpha abundances in M31 satellites (Vargas+, 2014)J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)J/MNRAS/444/1812 : M54 and Sgr dSph red giants abundances (Mucciarelli+, 2014)J/MNRAS/439/1015 : Velocities of red giants in 7 LG dwarf gal. (Kirby+, 2014)J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)J/AJ/146/46 : Star Formation Rate in nearby galaxies (Karachentsev+, 2013)J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013)J/ApJ/768/172 : Kinematic analysis of red giant in M31 dSphs (Collins+, 2013)J/AJ/144/134 : LITTLE THINGS survey of nearby dwarf galaxies (Hunter+, 2012)J/ApJ/756/74 : 2MASS view of Sgr dSph. VII. Kinematics (Frinchaboy+, 2012)J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)J/ApJ/752/45 : SPLASH: Stellar spectrosc. of M31 satellites (Tollerud+, 2012)J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)J/ApJ/711/361 : Local Group dE galaxies. II. (Geha+, 2010)J/ApJ/708/1290 : A 2MASS view of the Sgr dSph. VI. (Chou+, 2010)J/ApJ/706/599 : H{alpha} and UV SFR in the local volume (Lee+, 2009)J/AJ/137/3100 : Radial velocities of 4 dSph galaxies (Walker+, 2009)J/A+A/465/815 : Abundances of Sgr dSph stars (Sbordone+, 2007)J/AJ/128/2170 : H{alpha} imaging of irregular galaxies (Hunter+, 2004)J/AJ/123/3154 : RV light curves of variable stars in Leo A (Dolphin+, 2002)J/AJ/119/777 : BVRI photometry of Sagittarius DIG (Lee+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/834/9https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/834/9http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/834/9https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/834/9https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/834/9http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/834/9GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/834/9/table4 (Galaxy properties)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/834/9/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/834/9/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/834/9/table4?GETtext/xml+votable180.050000true149.8602530.74638890.005555555555555556Cone search capability for table J/ApJ/834/9/table2 (Radial velocities and membership)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/834/9/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/834/9/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/834/9/table2?GETtext/xml+votable180.050000true149.709333330.79433330.0055555555555555566/5287 5293 29699 48942 48943https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/834/9?format=asciiOpticalInfrareddefaultJ/ApJ/834/9/table4Galaxy propertiesSimbadNameSimbad column added by the CDSmeta.idchare_Mt/Mb[0.8/1.8] Negative uncertainty on Mt/Mbstat.errorfloatE_Mt/Mb[1/2.5] Positive uncertainty on Mt/Mbstat.error;stat.maxfloat[Fe/H][-1.9/-1.5] Average [Fe/H]phys.abund.Fe;stat.meanfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGalGalaxy namemeta.id;meta.maincharDist[827/1047] Distancekpcpos.distance;pos.heliocentricinte_Dist[11/53] Dist uncertaintykpcstat.errorintr_Dist[1/3] Distance reference (1)meta.ref;pos.frameintLV[1.7/6.6] Luminosity1e+06solLumphys.luminosityfloate_LV[0.2/1.4] LV uncertainty1e+06solLumstat.errorfloatr_LV[4/6] LV reference (1)meta.ref;pos.frameintrh[0.9/2.2] Half-light radius in arcminarcminphys.angSize;srcfloate_rh[0.03/0.2] rh uncertaintyarcminstat.errorfloatr_rh[4/6] rh reference (1)meta.ref;pos.frameintrhpc[277/517] Half-light radius in parsecpcphys.size.radiusinte_rhpc[16/29] rhpc uncertaintypcstat.errorintr_rhpc[4/6] rhpc reference (1)meta.ref;pos.frameintM*[1.5/3.3] Stellar mass1e+06solMassphys.massfloate_M*[0.2/0.7] M* uncertainty1e+06solMassstat.errorfloatr_M*[7] Stellar mass reference (1)meta.ref;pos.frameintSFRHa[0/9.3] H{alpha} star formation rate1e-05solMass.yr**-1phys.SFR;spect.linefloatr_SFRHaSFRHa reference(s) (1)meta.ref;pos.framecharSFRUV[0/7.2] UV star formation rate0.0001solMass.yr**-1meta.idfloatr_SFRUV[8/11] SFRUV reference (1)meta.ref;pos.frameintM(HI)[2.2/8.3] HI gas mass1e+06solMassphys.massfloate_M(HI)[0.3/1.2] M(HI) uncertainty1e+06solMassstat.errorfloatr_M(HI)[12] M(HI) reference (1)meta.ref;pos.frameintV(HI)[-140.3/23.7] HI velocitykm/sspect.dopplerVelocfloatr_V(HI)[12] V(HI) reference (1)meta.ref;pos.frameintsigHI[6.2/8.2] HI velocity dispersionkm/sphys.veloc.dispersion;spect.linefloatr_sigHI[12] sigHI reference (1)meta.ref;pos.frameintNm[25/127] Number of membersmeta.numberintNsNumber of sources in table 2meta.numberintnullableHRV[-142/27] Heliocentric velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[0.9/2] Negative uncertainty on HRVkm/sstat.errorfloatE_HRV[1/2] Positive uncertainty on HRVkm/sstat.error;stat.maxfloatVgsr[-30.7/6.2] GSR velocitykm/sphys.velocfloatsigma[7.8/9.4] Velocity dispersionkm/sphys.veloc.dispersionfloate_sigma[0.6/1.1] Negative uncertainty on sigmakm/sstat.errorfloatE_sigma[0.8/1.8] Positive uncertainty on sigmakm/sstat.error;stat.maxfloatM1/2[1.8/4] Mass within the half-light radius (2)1e+07solMassphys.massfloate_M1/2[0.3/0.4] Negative uncertainty on M1/21e+07solMassstat.errorfloatE_M1/2[0.4/0.4] Positive uncertainty on M1/21e+07solMassstat.error;stat.maxfloatM/L[10/21] Mass-to-light ratio within the half-light radiussolMass/solLumphys.composition.massLightRatiointe_M/L[3/4] Negative uncertainty on M/LsolMass/solLumstat.errorintE_M/L[3/6] Positive uncertainty on M/LsolMass/solLumstat.error;stat.maxintMt/Mb[4.4/9.6] Total (dynamical) mass divided by baryonic mass (3)phys.mass;arith.ratiofloate_[Fe/H][0.06/0.09] Positive uncertainty on [Fe/H]stat.error;phys.abund.FefloatE_[Fe/H][0.06/0.2] Negative uncertainty on [Fe/H]stat.error;stat.maxfloatpeffL[2.4/5.5] Effective yield (leaky box); in 10^-2^Z_{sun}_, see equation 3phys.composition.yieldfloate_peffL[0.4/1.1] Negative uncertainty on peffLstat.errorfloatE_peffL[0.4/1.2] Positive uncertainty on peffLstat.error;stat.maxfloatpeffP[2.4/5.3] Effective yield (pre-enriched); in 10^-2^Z_{sun}_, see equation 4phys.composition.yieldfloate_peffP[0.3/1.2] Negative uncertainty on peffPstat.errorfloatE_peffP[0.4/1.4] Positive uncertainty on peffPstat.error;stat.maxfloatl_[Fe/H]0Upper limit flag on [Fe/H]0meta.code.error;phys.abund.Fechar[Fe/H]0Initial metallicity of the gas for the pre-enriched modelphys.abund.Fefloate_[Fe/H]0[0.12]? [Fe/H]0 negative uncertaintystat.error;phys.abund.FefloatnullableE_[Fe/H]0[0.1]? [Fe/H]0 positive uncertaintystat.error;stat.maxfloatnullablef_[Fe/H]0[d] d: Upper limit with 95% confidencemeta.codechardlnPP[-1.8/12.2] {Delta}lnP value for the pre-enriched model (4)stat.paramfloatpeffA[2.1/4.4] Effective yield (accretion); in 10^-2^Z_{sun}_, see equations 5 & 6phys.composition.yieldfloate_peffA[0.3/0.7] Negative uncertainty on peffAstat.errorfloatE_peffA[0.3/0.8] Positive uncertainty on peffAstat.error;stat.maxfloatM[2.3/7.1] Accretion parameter M (5)stat.paramfloate_M[0.9/3.8] Negative uncertainty on Mstat.errorfloatE_M[1.9/6.2] Positive uncertainty on Mstat.error;stat.maxfloatdlnPA[-1.2/11.1] {Delta}lnP value for the accretion model (4)stat.paramfloatNEDNED column added by the CDSmeta.ref.urlchar_RAPositions from SIMBAD (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD (declination part)degpos.eq.dec;meta.mainJ/ApJ/834/9/table2Radial velocities and membershipSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGalDwarf galaxy abbreviation (1)src.class.starGalaxycharNameObject name (G1)meta.id;meta.maincharprimaryAmeta.ref.urlcharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainImag0[17.5/23.8] Extinction-corrected I band Vega magnitude (2)magphot.mag;em.opt.Ifloat(V-I)0[-0.6/3.6] Reddening-corrected (V-I) Vega color index (2)magphot.color;em.opt.V;em.opt.IfloatN[1/3] Number of masks for this targetmeta.numberintS/N[1/109] Signal-to-noise ratio (3)nm**-1stat.snrfloatHRV[-291/211]? Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloatnullablee_HRV[1/35]? Error on HRVkm/sstat.errorfloatnullableMm[NY] Membership in dwarf galaxymeta.code.member;src.class.starGalaxycharf_Mm? Reason(s) for non-membership (4)meta.codecharLCatDisplay Leo A data from Stonkute+, 2014, J/ApJS/214/19, within 0.5"meta.ref.urlintnullableKCatDisplay data from Kirby+, 2013, J/ApJ/779/102 and 2014, J/MNRAS/439/1015 within 0.5"meta.ref.urlintnullableSCatDisplay Sgr data from Momany+ 2014, J/A+A/572/A42; Beccari+, 2014, J/A+A/570/A78 and Boyer+, 2015, J/ApJS/216/10 within 1"meta.ref.urlintnullableJ/ApJ/834/9/table3Chemical abundancesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGalDwarf galaxy abbreviationsrc.class.starGalaxycharNameObject name (G1)meta.id;meta.maincharTeff[3984/4987] Effective temperatureKphys.temperature.effectiveintlog(g)[0.4/1.7] Surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H][-2.7/-0.5] Iron abundance relative to Sunlog(Sun)phys.abund.Fefloate_[Fe/H][0.1/0.5] Uncertainty in [Fe/H]log(Sun)stat.error;phys.abund.Fefloat[Mg/Fe][-0/1.2]? Magnesium-to-iron ratio relative to Sunlog(Sun)phys.abundfloatnullablee_[Mg/Fe][0.2/0.5]? Uncertainty in [Mg/Fe]log(Sun)stat.error;phys.abundfloatnullable[Si/Fe][-0.7/1.2]? Silicon-to-iron ratio relative to Sunlog(Sun)phys.abundfloatnullablee_[Si/Fe][0.2/0.5]? Uncertainty in [Si/Fe]log(Sun)stat.error;phys.abundfloatnullable[Ca/Fe][-0.8/1.1]? Calcium-to-iron ratio relative to Sunlog(Sun)phys.abundfloatnullablee_[Ca/Fe][0.1/0.5]? Uncertainty in [Ca/Fe]log(Sun)stat.error;phys.abundfloatnullable[Ti/Fe][-0.8/1.1]? Titanium-to-iron ratio relative to Sunlog(Sun)phys.abundfloatnullablee_[Ti/Fe][0.1/0.5]? Uncertainty in [Ti/Fe]log(Sun)stat.error;phys.abundfloatnullable[a/Fe][-0.8/1.2]? Alpha-to-iron ratio relative to Sunlog(Sun)phys.abundfloatnullablee_[a/Fe][0.1/0.5]? Uncertainty in [a/Fe]log(Sun)stat.error;phys.abundfloatnullable