J/A+A/665/A76ivo://CDS.VizieR/J/A+A/665/A76doi:10.26093/cds/vizier.36650076CDSComeron F.Djupvik A.A.Schneider N.2024-06-05T16:40:46Z2022-09-13T08:18:29ZCDS support team

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

cds-question@unistra.frstellar-associationsopen-star-clustersh-ii-regionsob-starspre-main-sequence-starsyoung-stellar-objectsW40 is a heavily obscured bipolar HII region projected in the direction of the Aquila Rift and ionized by hot stars in a central, partly embedded cluster. The study of the cluster and its surroundings has been greatly hampered thus far by the strong extinction in the region. We aim to improve the characterization of the W40 central cluster in terms of the census of its members and their spectral classification. We also search for other members of the region outside the central cluster, with particular interest in previously unidentified massive members that may contribute to the energy budget powering the expansion of the HII region. We use the Gaia eDR3 catalog to establish astrometric membership criteria based on the population of the W40 central cluster, reassess the distance of the region, and identify in this way new members, both inside and outside the cluster. We obtain visible spectroscopy in the red spectral region to classify both known and new members, complemented with Gaia and Spitzer photometry to assess the evolutionary status of the stellar population. Based on stars with high quality Gaia astrometry we derive a high-confidence geometric distance to the W40 region of 502pc+/-4pc and confirm the presence of a comoving extended population of stars at the same distance, spreading over the whole projected area of the HII region and beyond. Spectral classifications are presented for 21 members of the W40 region, 10 of them belonging to the central cluster. One of the newly identified B stars in the extended population is clearly interacting with the shell surrounding the HII region, giving rise to a small arc-shaped nebula that traces a bow shock. The infrared excess properties suggest that the extended population is significantly older (~3~Myr) than the W40 central cluster (<1~Myr). The area currently occupied by the W40 HII region and its surroundings has a history of star formation extending at least several million years in the past, of which the formation of the W40 central cluster and the subsequent HII region is one of the latest episodes. The newly determined distance suggests that W40 is behind, and physically detached from, a pervasive large dust layer which is some 60~pc foreground to it as determined by previous studies.2022A&A...665A..76Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/665/A76CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/350 : Gaia EDR3 (Gaia Collaboration, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/665/A76https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/665/A76http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/665/A76https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/665/A76https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/665/A76http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/665/A76GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/665/A76/table4 (Additional candidate members with relative proper motion less than 2 mas/yr and parallax between 1.0 and 3.0mas)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/665/A76/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/665/A76/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/665/A76/table4?GETtext/xml+votable180.050000true277.5609167-2.41172220.005555555555555556Cone search capability for table J/A+A/665/A76/table5 (Infrared photometry of high-confidence and candidate members)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/665/A76/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/665/A76/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/665/A76/table5?GETtext/xml+votable180.050000true277.5609167-2.41172220.0055555555555555566/30341 30343 30352 303547.952274030004205e-20 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/665/A76?format=asciidefaultJ/A+A/665/A76/table4Additional candidate members with relative proper motion less than 2 mas/yr and parallax between 1.0 and 3.0masrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectObject name (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainPlxGaia eDR3 Parallaxmaspos.parallaxfloate_PlxError in Parallaxmasstat.error;pos.parallaxfloatpmRAGaia eDR3 Proper motion in right ascensionmas/yrpos.pm;pos.eq.rafloate_pmRAError in proper motion in right ascensionmas/yrstat.error;pos.pm;pos.eq.rafloatpmDEGaia eDR3 Proper motion in declinationmas/yrpos.pm;pos.eq.decfloate_pmDEError in proper motion in declinationmas/yrstat.error;pos.pm;pos.eq.decfloatRUWEGaia eDR3 renormalized unit-weight errorstat.errorfloatBPmagGaia eDR3 Bp magnitudemagphot.mag;em.opt.Bfloate_BPmagError in Bp magnitudemagstat.error;phot.magfloatRPmagGaia eDR3 Rp magnitudemagphot.mag;em.opt.Rfloate_RPmagError in Rp magnitudemagstat.error;phot.magfloatKGF? Source number in Kuhn et al. (2010ApJ...725.2485K, Cat. J/ApJ/725/2485), [KGF2010] NNN in Simbadmeta.idintnullableSimbadNameSimbad column added by the CDSmeta.idcharnullableJ/A+A/665/A76/table5Infrared photometry of high-confidence and candidate membersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectObject name (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainJmag? J magnitudemagphot.mag;em.IR.Jfloatnullablee_Jmag? Error in the J magnitudemagstat.error;phot.magfloatnullableHmag? H magnitudemagphot.mag;em.IR.Hfloatnullablee_Hmag? Error in the H magnitudemagstat.error;phot.magfloatnullableKsmag? Ks magnitudemagphot.mag;em.IR.Kfloatnullablee_Ksmag? Error in the Ks magnitudemagstat.error;phot.magfloatnullableIRAC1mag? Spitzer IRAC I1 magnitudemagphot.mag;em.IR.3-4umfloatnullablee_IRAC1mag? Error in the Spitzer IRAC I1 magnitudemagstat.error;phot.magfloatnullableIRAC2mag? Spitzer IRAC I2 magnitudemagphot.mag;em.IR.4-8umfloatnullablee_IRAC2mag? Error in the Spitzer IRAC I2 magnitudemagstat.error;phot.magfloatnullable