J/A+A/669/A10ivo://CDS.VizieR/J/A+A/669/A10doi:10.26093/cds/vizier.36690010CDSZari E.Frankel N.Rix H.-W.2023-01-16T14:43:56Z2022-12-22T16:13:19ZCDS support team

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

cds-question@unistra.frmilky-way-galaxyearly-type-starsvisible-astronomyWe map the stellar age distribution (<~1Gyr) across a 6kpcx6kpc area of the Galactic disc, in order to constrain our Galaxy's recent star-formation history. Our modelling draws on the sample of Zari et al. (2021. Cat. J/A+A/650/A112) that encompasses all presumed disc OBA stars (~500000 sources) with G<16. To be less sensitive to reddening, we do not forward model the detailed CMD distribution of these stars, but instead the K-band absolute magnitude distribution, n(M_K_) among stars with M_K_<0 and T_eff_>7000K at a certain positions {vec}x in the disc as a step function with five age bins, b({tau}|{vec}x, {vec}{alpha}), logarithmically-spaced in age from {tau}=5Myr to {tau}~1Gyr. Given a set of isochrones and a Kroupa (2001) initial mass function, we sample b({tau},|{vec}x, {vec}{alpha}) to maximise the likelihood of the data n(M_K_|{vec}x, {vec}{alpha}), accounting for the selection function. This results in a set of mono-age stellar density maps across a sizeable portion of the Galactic disc. These maps show that some, but not all, spiral arms are reflected in overdensities of stars younger than 500Myr. The maps of the youngest stars (<10Myr) trace major star forming regions. The maps at all ages exhibit an outward density gradient and distinct spiral-like spatial structure, which is qualitatively similar on large scales among the five age bins. When summing over the maps' area and extrapolating to the whole disc, we find an effective star-formation rate over the last 10Myr of ~3.3M_{sun}_/yr, higher than previously published estimates that had not accounted for unresolved binaries. Remarkably, our stellar age distribution implies that the star-formation rate has been three times lower throughout most of the last Gyr, having risen distinctly only in the very recent past. Finally we use TNG50 simulations to explore how justified the common identification of local age distribution with global star formation history is: we find that the global star-formation rate at a given radius in Milky-Way-like galaxies is approximated within a factor of ~1.5 by the young age distribution within a 6kpcx6kpc area near R_{sun}_.2023A&A...669A..10Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/669/A10CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/650/A112 : Mapping hot luminous stars in the Galaxy (Zari+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/669/A10https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/669/A10http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/669/A10https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/669/A10https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/669/A10http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/669/A10GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/669/A10/table1alpha values and uncertainties for all the spaxelsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintxminMin x-coordinate of spaxelkpcpos.cartesian.x;instr.detdoublexmaxMax x-coordinate of spaxelkpcpos.cartesian.x;instr.detdoubleyminMin y-coordinate of spaxelkpcpos.cartesian.y;instr.detdoubleymaxMax y-coordinate of spaxelkpcpos.cartesian.y;instr.detdoublealpha1Best fit value of coefficient alpha_1yr**-1stat.fit.paramdoubleb_alpha116th percentile of coefficient alpha_1yr**-1stat.fit.param;stat.mindoubleB_alpha184th percentile of coefficient alpha_1yr**-1stat.fit.param;stat.maxdoublealpha2Best fit value of coefficient alpha_2yr**-1stat.fit.paramdoubleb_alpha216th percentile of coefficient alpha_2yr**-1stat.fit.param;stat.mindoubleB_alpha284th percentile of coefficient alpha_2yr**-1stat.fit.param;stat.maxdoublealpha3Best fit value of coefficient alpha_3yr**-1stat.fit.paramdoubleb_alpha316th percentile of coefficient alpha_3yr**-1stat.fit.param;stat.mindoubleB_alpha384th percentile of coefficient alpha_3yr**-1stat.fit.param;stat.maxdoublealpha4Best fit value of coefficient alpha_4yr**-1stat.fit.paramdoubleb_alpha416th percentile of coefficient alpha_4yr**-1stat.fit.param;stat.mindoubleB_alpha484th percentile of coefficient alpha_4yr**-1stat.fit.param;stat.maxdoublealpha5Best fit value of coefficient alpha_5yr**-1stat.fit.paramdoubleb_alpha516th percentile of coefficient alpha_5yr**-1stat.fit.param;stat.mindoubleB_alpha584th percentile of coefficient alpha_5yr**-1stat.fit.param;stat.maxdouble