J/A+A/649/A93ivo://CDS.VizieR/J/A+A/649/A93doi:10.26093/cds/vizier.36490093CDSBarbosa C.E.SpinielloC.Arnaboldi M.Coccato L.Hilker M.,Richtler T.2022-05-16T06:25:29Z2021-05-20T07:22:26ZCDS support team

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

cds-question@unistra.frgalaxy-clustersgalaxiesvisible-astronomychemical-abundancesMassive early-type galaxies are believed to be the end result of an extended mass accretion history. The stars formed in situ, very early during the initial phase of the assembly, might have originated from an extremely intense and rapid burst of star formation. These stars may still be found within the cores of such galaxies at z=0, depending on their accretion and merger histories. We wish to investigate the presence of a surviving high-z compact progenitor component in the brightest galaxy of the Hydra~I cluster, NGC~3311, by mapping its 2D kinematics and stellar population out to 2 effective radii. Our goal is to understand the formation of its several structural components and trace their mass assembly back in time. We combine MUSE observations, a customized and extended version of the state-of-the-art EMILES single stellar population models, and a newly developed parametric fully Bayesian framework to model the observed spectra using full-spectrum fitting. We present 2D maps, as well as radial profiles, of the stellar velocity dispersion, age, total metallicity, {alpha}-element, sodium abundance ([Na/Fe]), and the initial mass function slope. All properties have significant gradients, confirming the existence of multiple structural components, also including a "blue spot" characterized by younger and metal-richer stars. We find that the component dominating the light budget of NGC 3311 within R<2.0kpc, is the surviving z=0 analogue of a high-z compact core, according to the definition of Pulsoni et al. (2021). This concentrated structure has a relatively small velocity dispersion (sigma~180km/s), is very old (ages~11Gyr), metal-rich ([Z/H]~0.2 and [Na/Fe]~0.4), and has a bottom-heavy IMF (with slope Gamma_b_~2.4). In the outer region, instead, the line-of-sight velocity distribution becomes increasingly broader, and the stars have younger age. They are also metal and sodium poorer but {alpha}-element richer. The low-mass end of the IMF slope becomes Chabrier-like with increasing galactocentric distances. The existence of multiple structural components in NGC 3311 from photometry, kinematics, and stellar populations confirms the predictions from the two-phase formation scenario for NGC 3311, according to which a first very short, high-z star formation episode formed a compact stellar structure in its core, which then grew in size by the extended mass assembly of relatively massive satellites. Interestingly, the outer stellar population has an overabundant [alpha/Fe], most likely because NGC 3311, located at the center of the galaxy cluster, accreted stars from rapidly quenched satellites.2021A&A...649A..93Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/649/A93CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/589/A139 : Stellar populations of NGC 3311 (Barbosa+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/649/A93https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/649/A93http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/649/A93https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/649/A93https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/649/A93http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/649/A93GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/649/A93/table3Results of our worke_AvLower error of extinctionmagstat.errordoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDNumber of the Voronoi bin (fieldA_NNNN)meta.id;meta.maincharXProjected X coordinate relative to the center of NGC 3311( 1)kpcpos.cartesian.xdoubleYProjected Y coordinate relative to the center of NGC 3311 (1)kpcpos.cartesian.ydoubleRProjected radial distance relative to the center of NGC 3311 (1)kpcpos.distancedoublePA[] Position angle relative the centerdegpos.posAngdoubleSNRSignal-to-Noise ratio10nm**-1stat.snrdoubleGammabBimodal IMF slopestat.fit.paramdoublee_GammabLower error of IMF slopestat.errordoubleE_GammabUpper error of IMF slopestat.error;stat.maxdouble[Z/H]Total metallicitylog(Sun)phys.abund.Zdoublee_[Z/H]Lower error of metallicitylog(Sun)stat.error;src.redshiftdoubleE_[Z/H]Upper error of metallicitylog(Sun)stat.error;stat.maxdoubleAgeAge of stellar populationGyrtime.agedoublee_AgeLower error of ageGyrstat.error;time.agedoubleE_AgeUpper error of ageGyrstat.error;stat.maxdouble[alpha/Fe]Alpha-elements abundancelog(Sun)phys.abunddoublee_[alpha/Fe]Lower error of alpha abundancelog(Sun)stat.error;phys.abunddoubleE_[alpha/Fe]Upper error of alpha abundancelog(Sun)stat.error;stat.maxdouble[Na/Fe]Sodium abundancelog(Sun)phys.abunddoublee_[Na/Fe]Lower error of Na abundancelog(Sun)stat.error;phys.abunddoubleE_[Na/Fe]Upper error of Na abundancelog(Sun)stat.error;stat.maxdoubleAvTotal extinctionmagphys.absorptiondoubleE_AvUpper error of extinctionmagstat.error;stat.maxdoubleRvTotal-to-selective extinctionphys.absorptiondoublee_RvLower error of selective extinctionstat.errordoubleE_RvUpper error of selective extinctionstat.error;stat.maxdoubleVStellar systemic velocitykm/sphys.velocdoublee_VLower error of velocitykm/sstat.error;pos.cartesian.ydoubleE_VUpper error of velocitykm/sstat.error;stat.maxdoublesigmaStellar velocity dispersionkm/sphys.veloc.dispersiondoublee_sigmaLower error of velocity dispersionkm/sstat.errordoubleE_sigmaUpper error of velocity dispersionkm/sstat.error;stat.maxdoubleM/LMass-to-light ratio in the r-bandSunphys.composition.massLightRatiodoublee_M/LLower error in the mass-to-lightSunstat.errordoubleE_M/LUpper error in the mass-to-lightSunstat.error;stat.maxdoublealphaIMF mismatch parameterstat.fit.paramdoublee_alphaLower error of IMF mismatch parameterstat.error;pos.eq.radoubleE_alphaUpper error of IMF mismatch parameterstat.error;stat.maxdoublelogSigmaSurface stellar masslog(Sun.kpc**-2)phys.massdoublee_logSigmaLower error of surface stellar masslog(Sun.kpc**-2)stat.errordoubleE_logSigmaUpper error of surface stellar masslog(Sun.kpc**-2)stat.error;stat.maxdouble