J/ApJ/847/16ivo://CDS.VizieR/J/ApJ/847/16doi:10.26093/cds/vizier.18470016CDSBergemann M.Collet R.Schonrich R.Andrae R.Kovalev M.Ruchti G.,Hansen C.J.Magic Z.2018-09-25T13:12:59Z2018-06-27T09:15:04ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starschemical-abundancesline-intensitiesFrom exploratory studies and theoretical expectations it is known that simplifying approximations in spectroscopic analysis (local thermodynamic equilibrium (LTE), 1D) lead to systematic biases of stellar parameters and abundances. These biases depend strongly on surface gravity, temperature and, in particular, for LTE versus non-LTE (NLTE), on metallicity of the stars. Here we analyze the [Mg/Fe] and [Fe/H] plane of a sample of 326 stars, comparing LTE and NLTE results obtained using 1D hydrostatic models and averaged <3D> models. We show that compared to the <3D> NLTE benchmark, the other three methods display increasing biases toward lower metallicities, resulting in false trends of [Mg/Fe] against [Fe/H], which have profound implications for interpretations by chemical evolution models. In our best <3D> NLTE model, the halo and disk stars show a clearer behavior in the [Mg/Fe]-[Fe/H] plane, from the knee in abundance space down to the lowest metallicities. Our sample has a large fraction of thick disk stars and this population extends down to at least [Fe/H]~-1.6dex, further than previously proven. The thick disk stars display a constant [Mg/Fe]~0.3dex, with a small intrinsic dispersion in [Mg/Fe] that suggests that a fast SN Ia channel is not relevant for the disk formation. The halo stars reach higher [Mg/Fe] ratios and display a net trend of [Mg/Fe] at low metallicities, paired with a large dispersion in [Mg/Fe]. These indicate the diverse origin of halo stars from accreted low-mass systems to stochastic/inhomogeneous chemical evolution in the Galactic halo.2017ApJ...847...16Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/847/16CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIII/257 : RAVE second data release (Zwitter+, 2008)III/279 : RAVE 5th data release (Kunder+, 2017)I/337 : Gaia DR1 (Gaia Collaboration, 2016)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)J/A+A/511/L10 : Abundances and space velocities of 94 stars (Nissen+, 2010)J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)J/A+A/530/A54 : Abundances of 650 bulge red giants (Gonzalez+, 2011)J/ApJ/737/9 : RAVE data of stars in the thick disk (Ruchti+, 2011)J/A+A/546/A90 : NLTE analysis of Sr lines (Bergemann+, 2012)J/A+A/557/A26 : STAGGER-grid of 3D stellar models. I. (Magic+, 2013)J/MNRAS/429/126 : Atmospheric parameters from Fe lines (Ruchti+, 2013)J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014)J/A+A/572/A10 : (BV) photometry in Carina dSph (de Boer+, 2014)J/A+A/572/A88 : Measured EWs for Fornax RGB stars (Lemasle+, 2014)J/AJ/148/81 : APASS BVgri photometry of RAVE stars. I. Data (Munari+, 2014)J/A+A/584/A46 : GIRAFFE Inner Bulge Survey (GIBS). II. (Gonzalez+, 2015)J/AJ/151/144 : Weights for 15 APOGEE chemical elements (Garcia+, 2016)J/ApJ/819/2 : APOGEE kinematics. I. Galactic bulge overview (Ness+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/847/16https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/847/16http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/847/16https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/847/16https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/847/16http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/847/16GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/847/16/stars (Stellar parameters and derived Mg abundances and equivalent widths for the stellar (tables 1 and 3))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/847/16/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/847/16/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/847/16/stars?GETtext/xml+votable180.050000true5.8778306-16.52864440.0055555555555555566/16504 16586 16607 16764 16819 16828 16890 16907 16929 17033 17091 17127 17134 17234 17517 17556 17595 17618 17698 18606 18683 18952 18973 20527 20538 20623 20635 20882 21126 21202 21228 21229 21241 22564 23043 23304 24602 24607 24618 24636 24644 24663 24668 24675 24717 24750 24887 24986 24994 25061 25074 25098 25126 25139 25158 25167 25197 25207 25297 25318 25327 25350 25394 25400 25405 25520 25595 25608 25614 25618 25622 25624 25635 25652 25696 25767 25786 25857 25873 25893 25938 25990 26145 26168 26241 26669 26720 26722 26725 26728 26730 26739 26764 26767 26827 26925 26927 27016 27182 30761 30778 30857 30870 30923 30962 31117 31249 32894 33030 33051 33121 33142 33207 33366 33446 33521 33523 33720 33724 33750 33877 33885 34141 34260 34276 34370 34427 34478 34493 34570 34588 34610 34908 34935 34939 35084 35090 35112 35234 35267 35288 35359 35381 35649 35760 35857 35927 35947 36002 36082 36105 36172 36263 36316 36336 36446 36467 36486 36501 36710 36728 36783 36842 36995 37543 37551 38218 38303 38336 38639 38683 38772 38775 38779 38780 38851 39084 39188 39443 39490 39653 39707 39817 39847 39866 40046 40133 40270 40278 40313 40337 40498 40911 41029 43248 43307 43487 43508 43577 43619 43629 43663 43862 43905 43950 43976 43992 44002 44006 44208 44260 44279 44458 44478 44552 44641 44661 44701 44754 44780 44817 44825 44830 44841 44847 44851 44852 44890 44901 44906 44923 44960 45019 45037 45097 45185 45199 45216 45408 45595 45622 45640 45658 45714 45748 45764 45786 45804 45807 45857 45954 46023 46167 46203 46250 46273 46324 46370 46418 46633 46666 46696 46706 46806 46942 46987 47094 47168 47191 47201 47223 47226 47325 47373 47379 47387 47400 47447 47544 47564 47589 47711 47895 47940 47954 47967 48087 48163 48171 48186 48246 48256 48272 48281 48358 48436 48588 48609 48641 48648 48672 48676 48677 48694 48749 48750 48751 48752 48861 49093 49103 49124https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/847/16?format=asciidefaultJ/ApJ/847/16/starsStellar parameters and derived Mg abundances and equivalent widths for the stellar (tables 1 and 3)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSimbad data-base identifiermeta.id;meta.datasetcharTeff1[4004/6531] LTE-Fe effective temperatureKphys.temperature.effectiveintlog(g)1[0.5/4.4] LTE-Fe surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H]1[-3.2/-0.3] LTE-Fe metallicitylog(Sun)phys.abund.ZfloatV1[0.5/3] LTE-Fe microturbulencekm/sphys.veloc.microTurbfloatTeff2[4043/6519] NLTE-Opt effective temperatureKphys.temperature.effectiveintlog(g)2[0.5/4.6] NLTE-Opt surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H]2[-2.8/-0.4] NLTE-Opt metallicitylog(Sun)phys.abund.ZfloatV2[0.5/3.3] NLTE-Opt microturbulencekm/sphys.veloc.microTurbfloat[Mg]1[-0.03/0.7]? Log Mg/Fe abundance ratio: 1D LTElog(Sun)phys.abundfloatnullablee_[Mg]1[0.1/0.3]? Uncertainty in [Mg]1log(Sun)stat.errorfloatnullable[Mg]2[-0.02/0.7]? Log Mg/Fe abundance ratio: NLTE-opt & LTE Mglog(Sun)phys.abundfloatnullablee_[Mg]2[0.1/0.3]? Uncertainty in [Mg]2log(Sun)stat.errorfloatnullable[Mg]3[-0.04/0.6]? Log Mg/Fe abundance ratio: NLTE-opt & NLTE Mglog(Sun)phys.abundfloatnullablee_[Mg]3[0.1/0.3]? Uncertainty in [Mg]3log(Sun)stat.errorfloatnullable[Mg]4[0.02/0.6]? Log Mg/Fe abundance ratio: NLTE-opt & <3D> NLTE Mglog(Sun)phys.abundfloatnullablee_[Mg]4[0.1/0.3]? Uncertainty in [Mg]4log(Sun)stat.errorfloatnullableFlag[0/2]? Number of measured Mg I lines (1)meta.code.errorintnullablePop[1/3] Galactic population assignmentsrc.classfloatEW1[41.9/267.1]? Equivalent width of the 552.8nm MgI line1e-13mspect.line.eqWidth;em.opt.VfloatnullableEW2[2.3/143.5]? Equivalent width of the 571.1nm MgI line1e-13mspect.line.eqWidth;em.opt.VfloatnullableRAVEDisplay data from RAVE DR5 (Kunder+, 2017, III/279) within 0.5"meta.ref.urlcharR13Display data from Ruchti+, 2013, J/MNRAS/429/126, within 1"meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main