J/A+A/608/A148ivo://CDS.VizieR/J/A+A/608/A148doi:10.26093/cds/vizier.36080148CDSZari E.Brown A.G.A.de Bruijne J.Manara C.F.de Zeeuw P.T.2018-03-01T08:30:54Z2017-12-19T08:11:08ZCDS support team

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

cds-question@unistra.frstellar-associationspre-main-sequence-starsinfrared-photometryvisible-astronomytrigonometric-parallaxproper-motionsIn this work we use the first data release of the Gaia mission to explore the three-dimensional arrangement and age ordering of the many stellar groups toward the Orion OB association, aiming at a new classification and characterization of the stellar population not embedded in the Orion A and B molecular clouds. We make use of the parallaxes and proper motions provided in the Tycho Gaia Astrometric Solution (TGAS) subset of the Gaia Data Release 1 (DR1) catalog and of the combination of Gaia DR1 and 2MASS photometry. In TGAS, we find evidence for the presence of a young population at a parallax {varpi}~2.65mas, which is loosely distributed around the following known clusters: 25 Ori, {epsilon} Ori, and {sigma} Ori, and NGC 1980 ({iota} Ori) and the Orion Nebula Cluster (ONC). The low mass counterpart of this population is visible in the color magnitude diagrams constructed by combining Gaia DR1 G-band photometry and 2MASS. We study the density distribution of the young sources in the sky using a kernel density estimation (KDE). We find the same groups as in TGAS and also some other density enhancements that might be related to the recently discovered Orion X group, Orion dust ring, and {lambda} Ori complex. The maps also suggest that the 25 Ori group presents a northern elongation.We estimated the ages of this population using a Bayesian isochronal fitting procedure assuming a unique parallax value for all the sources, and we inferred the presence of an age gradient going from 25 Ori (13-15Myr) to the ONC (1-2Myr). We confirmed this age ordering by repeating the Bayesian fit using the Pan-STARRS1 data. Intriguingly, the estimated ages toward the NGC 1980 cluster span a broad range of values. This can either be due to the presence of two populations coming from two different episodes of star formation or to a large spread along the line of sight of the same population. Some confusion might arise from the presence of unresolved binaries, which are not modeled in the fit, and usually mimic a younger population. Finally, we provisionally relate the stellar groups to the gas and dust features in Orion. Our results form the first step toward using Gaia data to unravel the complex star formation history of the Orion region in terms of the various star formation episodes, their duration, and their effects on the surrounding interstellar medium.2017A&A...608A.148Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/608/A148CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/337 : Gaia DR1 (Gaia Collaboration, 2016)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/608/A148https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/608/A148http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/608/A148https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/608/A148https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/608/A148http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/608/A148GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/608/A148/origaia (Gaia DR1 sources in the Orion field)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/608/A148/origaia?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/608/A148/origaia?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/608/A148/origaia?GETtext/xml+votable180.050000true83.608741201515.21949687310.005555555555555556Cone search capability for table J/A+A/608/A148/x2mass (Gaia DR1 sources cross-matched with the 2MASS catalogue, with separation < 1")https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/608/A148/x2mass?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/608/A148/x2mass?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/608/A148/x2mass?GETtext/xml+votable180.050000true83.60874285977415.219494892580.005555555555555556Cone search capability for table J/A+A/608/A148/oritgas (TGAS sources in the Orion field)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/608/A148/oritgas?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/608/A148/oritgas?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/608/A148/oritgas?GETtext/xml+votable180.050000true80.9732339984-17.63662167260.0055555555555555562/89 3/334-335 368 370 4/1324-1325 1327 1331 1334-1335 1384 1386 1413 1457 1460-1461 1486 5/5278-5279 5305 5307 5321-5323 5330-5331 5334-5335 5504 5506 5512 5514-5515 5542 5548 5550 5661 5663 5685 5825 5827 5914 5936 5938-5939 6016-6017 6020-6021 6032 6/21102-21103 21111 21217 21219 21275 21278-21279 21282-21283 21330-21331 21333-21335 22028 22030 22052 22054-22055 22074 22160 22162 22198 22204 22206-22207 22597 22599 22640-22641 22643 22649 22749 22751 22773 23297 23299 23305 23307 23332-23333 23344-23345 23348-23349 23624 23626 23648 23650-23651 23662 23748 23750 23794 23800 23802 24072-24073 24076-24077 24088-24089 24132-24134 241448.650015785639275e-20 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/608/A148?format=asciiInfraredOpticaldefaultJ/A+A/608/A148/origaiaGaia DR1 sources in the Orion fieldrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSourceSource ID (source_id)meta.idRA_ICRSGaia right ascension (ICRS) at epoch 2015.0 (ra)degpos.eq.ra;meta.mainindexedDE_ICRSGaia declination (ICRS) at epoch 2015.0 (dec)degpos.eq.dec;meta.mainindexedGLONGaia Galactic longitude at epoch 2015.0 (l)degpos.galactic.lonGLATGaia Galactic latitude at epoch 2015.0 (b)degpos.galactic.latdouble<Gmag>Gaia G-band mean magnitude (phot_g_mean_mag)magphot.mag;em.opt.Rfloat<FG>Gaia G-band mean flux (phot_g_mean_flux)phot.flux.density;em.opt.Rdoublee_<FG>Error on G-band mean flux (phot_g_mean_flux_error)stat.errordoublepmRA? Gaia proper motion in right ascension direction (pmra)mas/yrpos.pm;pos.eq.radoublenullablepmDE? Gaia proper motion in declination direction (pmdec)mas/yrpos.pm;pos.eq.decdoublenullablePlx? Gaia Absolute barycentric stellar parallax (parallax)maspos.parallaxfloatnullablee_pmRA? Standard error of pmRA (pmra_error)mas/yrstat.error;pos.pm;pos.eq.rafloatnullablee_pmDE? Standard error of pmDE (pmdec_error)mas/yrstat.error;pos.pm;pos.eq.decfloatnullablee_Plx? Standard error of Plx (parallax_error)masstat.error;pos.parallaxfloatnullable_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into account (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into account (computed by VizieR, not part of the original data)degpos.eq.decnullableindexedJ/A+A/608/A148/x2massGaia DR1 sources cross-matched with the 2MASS catalogue, with separation < 1"recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSourceGaia Source ID (source_id)meta.idGLONGaia Galactic longitude at epoch 2015.0 (l)degpos.galactic.lonindexedGLATGaia Galactic latitude at epoch 2015.0 (b)degpos.galactic.latindexed<Gmag>Gaia G-band mean magnitude (phot_g_mean_mag)magphot.mag;em.opt.Rfloate_<FG>Error on G-band mean flux (phot_g_mean_flux_error)stat.errordouble<FG>Gaia G-band mean flux (phot_g_mean_flux)phot.flux.density;em.opt.RdoubleJmag2MASS J magnitude (j_m)magphot.mag;em.IR.Jfloate_Jmag? Error on Jmag (j_msigcom)magstat.error;phot.mag;em.IR.JfloatnullableHmag? 2MASS H magnitude (h_m)magphot.mag;em.IR.Hfloatnullablee_Hmag? Error on Hmag (h_msigcom)magstat.error;phot.mag;em.IR.HfloatnullableKsmag? 2MASS Ks magnitude (ks_m)magphot.mag;em.IR.Kfloatnullablee_Ksmag? Error on Ksmag (ks_msigcom)magstat.error;phot.mag;em.IR.KfloatnullableQual2MASS quality flags (ph_qual)meta.code.qualchar_RA.icrsRight ascension (ICRS) at Epoch=J2015. (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015. (computed by VizieR, not part of the original data)degpos.eq.decnullableindexedJ/A+A/608/A148/oritgasTGAS sources in the Orion fieldrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHIP? HIP number (hip)meta.id;meta.mainintnullableSourceGaia Source ID (source_id)meta.idRA_ICRSGaia right ascension (ICRS) at epoch 2015.0 (ra)degpos.eq.ra;meta.mainindexedDE_ICRSGaia declination (ICRS) at epoch 2015.0 (dec)degpos.eq.dec;meta.mainindexedGLONGaia Galactic longitude at epoch 2015.0 (l)degpos.galactic.lonGLATGaia Galactic latitude at epoch 2015.0 (b)degpos.galactic.latdouble<Gmag>Gaia G-band mean magnitude (phot_g_mean_mag)magphot.mag;em.opt.Rfloat<FG>Gaia G-band mean flux (phot_g_mean_flux)phot.flux.density;em.opt.Rdoublee_<FG>Error on G-band mean flux (phot_g_mean_flux_error)stat.errordoublepmRAGaia proper motion in right ascension direction (pmra)mas/yrpos.pm;pos.eq.radoublepmDEGaia proper motion in declination direction (pmdec)mas/yrpos.pm;pos.eq.decdoublePlxGaia Absolute barycentric stellar parallax (parallax)maspos.parallaxfloate_pmRAStandard error of pmRA (pmra_error)mas/yrstat.error;pos.pm;pos.eq.rafloate_pmDEStandard error of pmDE (pmdec_error)mas/yrstat.error;pos.pm;pos.eq.decfloate_PlxStandard error of Plx (parallax_error)masstat.error;pos.parallaxfloat_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into account (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into account (computed by VizieR, not part of the original data)degpos.eq.decnullableindexed