J/A+A/523/A23ivo://CDS.VizieR/J/A+A/523/A23doi:10.26093/cds/vizier.35230023CDSGarcia M.Herrero A.Castro N.Corral L.Rosenberg A.2014-08-03T21:21:37Z2014-07-23T12:47:22ZCDS support team

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

cds-question@unistra.frgalaxiesstellar-associationsob-starsTo understand the structure and evolution of massive stars, systematic surveys of the Local Group galaxies have been undertaken, to find these objects in environments of different chemical abundances. We focus on the metal-poor irregular galaxy IC 1613 to analyze the stellar and wind structure of its low-metallicity massive stars. We ultimately aim to study the metallicity-dependent driving mechanism of the winds of blue massive stars and use metal-poor massive stars of the Local Volume as a proxy for the stars in the early Universe. In a previous paper we produced a list of OB associations in IC 1613. Their properties are not only a powerful aid towards finding the most interesting candidate massive stars, but also reveal the structure and recent star formation history of the galaxy. We characterize these OB associations and study their connection with the galactic global properties. The reddening-free Q parameter is a powerful tool in the photometric analysis of young populations of massive stars, since it exhibits a smaller degree of degeneracy with OB spectral types than the B-V color. The color-magnitude diagram (Q vs. V) of the OB associations in IC 1613 is studied to determine their age and mass, and confirm the population of young massive stars. We identified more than 10 stars with M>=50M_{sun}_. Spectral classification available for some of them confirm their massive nature, yet we find the common discrepancy with the spectroscopically derived masses. There is a general increasing trend of the mass of the most massive member with the number of members of each association, but not with the stellar density. The average diameter of the associations of this catalog is 40pc, half the historically considered typical size of OB associations. Size increases with the association population. The distribution of the groups strongly correlates with that of neutral and ionized hydrogen. We find the largest dispersion of association ages in the bubble region of the galaxy where hydrogen is abundant, implying that recent star formation has proceeded over a longer period of time than in the rest of the galaxy, and is still ongoing. Very young associations are found at the west of the galaxy far from the bubble region, traditionally considered the sole locus of star formation, but still rich in neutral hydrogen. The contrast in the stellar properties derived from photometry and spectroscopy (when the latter is available) shows that the Q pseudo-color is very useful for estimating the parameters of OB stars when only photometric observations exist. This work helped define an extensive pool of candidate OB stars for subsequent spectroscopic analyses designed to study the structure and winds of metal-poor massive stars.2010A&A...523A..23Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/523/A23CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/502/1015 : OB associations in IC 1613 (Garcia+, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/523/A23https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/523/A23http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/523/A23https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/523/A23https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/523/A23http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/523/A23GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/523/A23/table1 (Properties of OB associations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/523/A23/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/523/A23/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/523/A23/table1?GETtext/xml+votable180.050000true16.1022152.110538890.0055555555555555566/18041https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/523/A23?format=asciiOpticaldefaultJ/A+A/523/A23/table1Properties of OB associationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintf_ID[?l*+- ] Dubious association (6)meta.codecharIDOB association identification numbermeta.id;phys.atmol.numberintn_ID[n] n indicates a note in notes.dat filemeta.notecharRAJ2000Right ascension (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (1)degpos.eq.dec;meta.mainNOB[0/69] Number of OB members (NOB) used in age and mass determination of the association (2)meta.numberintRadRadius estimate (3)arcsecphys.angSize;srcfloatSigmaStellar surface density (Sigma=NOB/({pi}R^2^)pc**-2stat.stdev;src.densitydouble<dmin>Distance of each OB member to its closest neighbor, averaged over the associationarcsecpos.angDistancefloatlogA0? Lower value of logAge interval (4)log(yr)time.agefloatnullablelogA1? Upper value of logAge interval (4)log(yr)time.agefloatnullableMup0[7/77]? Initial stellar mass (5)solMassphys.massintnullableMup[7/77]? Current stellar mass (5)solMassphys.massintnullableE(B-V)? Average value of extinction towards the bona-fide members of the association (7)magphot.color.excessfloatnullablee_E(B-V)? Standard deviation of the extinction towards the members of the association (8)magstat.errorfloatnullableMtot? Total mass of the association (9)solMassmeta.id.assoc;phys.massfloatnullableSpTypeKnown spectral types for members, from Bresolin et al. (2007ApJ...671.2028B)src.spTypecharJ/A+A/523/A23/notesIndividual notesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDOB association identification numbermeta.id;phys.atmol.numberintNoteText of the notemeta.notechar