J/A+A/673/A18ivo://CDS.VizieR/J/A+A/673/A18doi:10.26093/cds/vizier.36730018CDSGiribaldi R.E.Smiljanic R.2024-11-06T20:03:59Z2023-04-24T10:41:52ZCDS support team

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

cds-question@unistra.frlate-type-starsstellar-agesOver its history, the Milky Way has accreted several smaller satellite galaxies. These mergers added stars and gas to the Galaxy and affected the properties of the pre-existing stellar populations. Stellar chemical abundances and ages are needed to establish the chronological order of events that occur before, during, and after such mergers. We report the precise ages (~6.5%) and chemical abundances for the Titans, a sample of old metal-poor dwarfs and subgiants with accurate atmospheric parameters. We also obtain their ages with an average precision of 10% for a selected sample of dwarf stars from the GALAH survey. We use these stars, located within ~1 kiloparsec of the Sun, to analyse the chronology of the chemical evolution of in situ and accreted metal-poor stellar populations. We determined ages via isochrone fitting. For the Titans, we determined abundances of Mg, Si, Ca, Ti, Ni, Ba, and Eu using spectrum synthesis. The [Mg/Fe] abundances of the GALAH stars were re-scaled to be consistent with the abundances of the Titans. We separated stellar populations by primarily employing chemical abundances and orbits. We find that star formation in the so-called Gaia-Enceladus or Gaia-Sausage galaxy, the last major system to merge with the Milky Way, lasted at least 3 billion years and got truncated 9.6+/-0.2 billion years ago. This marks with a very high level of precision the last stage of its merging process. We also identified stars of a heated metal-poor in-situ population with virtually null net rotation, probably disturbed by several of the early Milky Way mergers. We show that this population is more metal-rich than Gaia-Enceladus at any moment in time. The sequence of events uncovered in our analysis supports the hypothesis that Gaia-Enceladus truncated the formation of the high-{alpha} disc and caused the gas infall that forms the low-{alpha} disc. This finding is in agreement with theoretical predictions.2023A&A...673A..18Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/673/A18CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)J/A+A/650/A194 : Titans metal-poor reference stars. I. (Giribaldi+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/673/A18https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/673/A18http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/673/A18https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/673/A18https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/673/A18http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/673/A18GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/673/A18/titans (Titans parameter set ADS (complements the table J/A+A/650/A194/table2))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/673/A18/titans?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/673/A18/titans?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/673/A18/titans?GETtext/xml+votable180.050000true112.671924.08620.005555555555555556Cone search capability for table J/A+A/673/A18/select (Selected stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/673/A18/select?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/673/A18/select?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/673/A18/select?GETtext/xml+votable180.050000true112.672708624.08517640.0055555555555555565/8416 6/373 404 476 4251 4280 4287 4328 4376 4680 4732 4874 5195 6159 8999 12361 12704 12793 16631 16645 17026 17124 17509 17545 18019 18115 18436 18449 18455 18459 18536 18586 18621 18627 18887 19332 19342 20495 20542 20600 20705 21080 21109 21157 21829 21840 22420 22727 22755 22996 23011 23015 23096 23132 24580 24606 24692 24722 24777 24837 25228 25385 25423 25456 25549 25576 25643-25644 25646 25691 25710 26025 26254 26284 26289 26901 27030-27031 27047 27051 27054 27056 27176 27180 27394 27407 27537 27681 27785 27857 28336 28844 29009 29245 29357 29417 29765 30179 30950 32846 32949 32968 32981 33018 33034 33086 33241 33302 33318 33350 33377 33396 33421 33436 33462 33473 33498 33579 33794 33831 33921 34095 34251 34538 34682-34684 34848 34862 34947 35913 36084 36745 37057 37417 37437 37540 37769 38072 38102 38216 38489 38602 38795 38797 38799 38842 38855 38917 38960 39010 39446 39555 39575 39593 39647 39692 39714 40261 40338 40567 40655 40697 40833 40859 40996 41192 41259 41273 41318 41348 42252 42331 42698 42732 42909 42924 43126 43218 43251 43359 43407 43445 43457 43472 43589 43603 43786 43804 43842 43907 43916 43960 43984 44098 44152 44173 44281 44319 44392 44418 44519 44522 44542 44653 45312 45321 45351 45357 45361 45372 45375 45378 45380 45384 45455 45723 45905 45911 46029 46055 46506 46625 46631 46774 46828 47040 47147 47149 47166 47257 47325 47360 47401 47411 47416 47466 47511 47570 47784 47799 47804 48257 48281 48394 48423 48719 48736 48969 490491.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/673/A18?format=asciidefaultJ/A+A/673/A18/titansTitans parameter set ADS (complements the table J/A+A/650/A194/table2)B_MassMass at upper 1 sigma limitsolMassphys.massfloatRMost probable radiussolRadphys.size.radiusfloatb_RRadius at lower 1 sigma limitsolRadphys.size.radiusfloatB_RRadius at upper 1 sigma limitsolRadphys.size.radiusfloatGmagGaia G magnitudemagphot.mag;em.optfloatBPmagGaia Bp magnitudemagphot.mag;em.opt.BfloatRPmagGaia Rp magnitudemagphot.mag;em.opt.Rfloat_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.raindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.decindexedSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarSimbad star namemeta.id;meta.maincharRAICRSRight ascension (ICRS, epoch J2000)degpos.eq.ra;meta.mainDEICRSDeclination (ICRS, epoch J2000)degpos.eq.dec;meta.mainVmagVisual magnitude in Johnson systemmagphot.mag;em.opt.VfloatPlxGaia DR3 parallaxmaspos.parallaxfloatpmRAProper motion in right ascension (ICRS, epoch J2000) form Gaia DR3mas/yrpos.pm;pos.eq.radoublepmDEProper motion in declination (ICRS, epoch J2000) form Gaia DR3mas/yrpos.pm;pos.eq.decdoublee_PlxGaia DR3 parallax errormasstat.error;pos.parallaxfloatHVHeliocentric velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HVHeliocentric velocity errorkm/sstat.errorfloat[Ti/Fe]Titanium to iron ratio relative to the Sunphys.abundfloat[Mg/Fe]Magnesium to iron ratio relative to the Sunphys.abundfloate_[Mg/Fe]Magnesium to iron ratio errorstat.error;phys.abundfloat[Si/Fe]? Silicon to iron ratio relative to the Sunphys.abunddoublenullable[Ca/Fe]? Calcium to iron ratio relative to the Sunphys.abunddoublenullable[Ni/Fe]? Nickel to iron ratio relative to the Sunphys.abunddoublenullable[Eu/Fe]? Europium to iron ratio relative to the Sunphys.abunddoublenullable[Ba/Fe]? Barium to iron ratio relative to the Sunphys.abund.Fe;arith.ratiodoublenullablee_[Ba/Fe]? Barium to iron ratio errorstat.error;phys.abunddoublenullablediffCorDifussion correctionarith.factorfloatAgeMost probable ageGyrtime.agefloatb_AgeAge at lower 1 sigma limitGyrtime.agefloatB_AgeAge at upper 1 sigma limitGyrtime.agefloatMassMost probable masssolMassphys.massfloatb_MassMass at lower 1 sigma limitsolMassphys.massfloatJ/A+A/673/A18/selectSelected starsSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar name (1)meta.id;meta.maincharGaiaDR2Gaia DR2 identifiermeta.idTeffEffective temperatureKphys.temperature.effectiveintloggSurface gravitylog(cm.s**-2)phys.gravityfloatAgeStellar ageGyrtime.agefloate_Age1 sigma error towards lower ageGyrstat.error;time.agefloatE_Age1 sigma error towards higher ageGyrstat.error;stat.maxfloat[Fe/H]Metallicity or iron to hydrogen ratiophys.abund.Zfloat[Mg/Fe]Magnesium to iron ratio relative to the Sunphys.abundfloatPopMembership ascription to a Galactic population in the halometa.code.memberchar_RAPositions from Gaia DR2 (right ascension part)degpos.eq.ra;meta.main_DEPositions from Gaia DR2 (declination part)degpos.eq.dec;meta.main