J/AJ/144/142ivo://CDS.VizieR/J/AJ/144/142doi:10.26093/cds/vizier.51440142CDSBianchi L.Efremova B.Hodge P.Kang Y.2018-01-26T07:38:00Z2013-12-19T06:56:09ZCDS support team

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

cds-question@unistra.frgalaxieshst-photometryearly-type-starsWe studied the young stellar populations of 22 star-forming regions in the Andromeda galaxy (M31), with Hubble Space Telescope (HST) multi-band imaging from far-UV to I. The regions were selected from Galaxy Evolution Explorer (GALEX) wide-field far-UV imaging; they sample different environments and galactocentric distances from 6 to 22kpc. They were imaged with 30 HST fields (360 distinct images, in six bandpasses), with a pixel scale of 0.38pc projected on the sky, at the distance of M31. This study is part of HST treasury survey program HST-GO-11079, which includes star-forming regions in eight Local Group galaxies. We provide a merged catalog of six-band stellar photometry in the 30 M31 fields, containing 118036 sources brighter than V and B~23mag. Each HST field covers about 0.3kpc^2^ in M31, and contains up to ~7000 stars, of which the number varies by a factor of >7 among the target regions; a large fraction of the sample are hot massive stars, due to our choice of filters and exposures. We derived stellar physical parameters and interstellar extinction for individual sources by spectral energy distribution analysis with model-atmosphere colors, and used the results to infer ages, massive stars content, and extinction of the star-forming regions. Reddening is up to E(B-V)<~0.6mag in some OB associations, and lowest in the outermost regions (average of <~0.12mag in OB184 at 21.9kpc). We examined the spatial distribution (clustering) of the hot massive stars, and defined OB associations on various spatial scales from compact to wider, more spread out ones. A hierarchical structuring is observed, with small compact groups arranged within large complexes. Their areas vary from less than 10 to 10^5^pc^2^, and masses are up to {approx}10^5^M_{sun}_, in the scales sampled by our analysis. Their cumulative mass distribution follows a power law, at least in part of the sampled regime. Hot-star counts in the young regions compare very well with integrated measurements of UV flux from GALEX.2012AJ....144..142Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/144/142CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)J/AJ/143/74 : HST photometry in 6 dwarf galaxies (Bianchi+, 2012)J/ApJS/199/37 : GALEX catalog of star clusters in M31 (Kang+, 2012)J/ApJ/730/88 : NGC 6822 star-forming regions from UV data (Efremova+, 2011)J/ApJ/703/614 : UV star-forming regions in M31 (Kang+, 2009)J/ApJS/173/185 : GALEX ultraviolet atlas of nearby galaxies (Gil de Paz+, 2007)J/PASP/119/7 : HST WFPC2 star clusters in M31 (Krienke+, 2007)J/AJ/133/2393 : UBVRI phot. in 7 Local Group dwarfs galaxies (Massey+, 2007)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/ApJS/154/623 : M31 Long Period Variables : Photometry (Mould+, 2004)J/AJ/122/2458 : M31 globular clusters from HST (Barmby+, 2001)J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)J/A+A/278/36 : M 31 new OB associations (Magnier+ 1993)http://dolomiti.pha.jhu.edu/LocalGroup : Results from HST program 11079https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/144/142https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/144/142http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/144/142https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/144/142https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/144/142http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/144/142GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/144/142/table1 (HST observations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/144/142/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/144/142/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/144/142/table1?GETtext/xml+votable180.050000true11.04458341.552833060.005555555555555556Cone search capability for table J/AJ/144/142/table2 (HST photometry catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/144/142/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/144/142/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/144/142/table2?GETtext/xml+votable180.050000true9.366183340.0253220.0055555555555555566/2622 2623 2666 2667 2705 2708 2709 27522.0401237512456292e-19 1.3189343879298211e-18https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/144/142?format=asciiOpticaldefaultJ/AJ/144/142/table1HST observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFrVisit/field (1)obs.fieldcharprimaryFieldField namemeta.id.parentcharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainDistGalactocentric distancekpcpos.distancefloatT1Exposure time in F170Wstime.expocharT2Exposure time in F255Wstime.expocharT3Exposure time in F336Wstime.expocharT4Exposure time in F439Wstime.expocharT5Exposure time in F555Wstime.expocharT6Exposure time in F814Wstime.expocharJ/AJ/144/142/table2HST photometry catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[0/118035] Running sequence number <[BEH2012] M31 NNNNNN> in Simbadmeta.id;meta.mainintIAUSource IAU identifier (JHHMMSS.s+DDMMSS)meta.idcharRAJ2000Right Ascension in decimal degrees (J2000) (1)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000) (1)degpos.eq.dec;meta.mainindexedF170W? HST/WFPC2 F170W band Vega magnitude (2)magphot.mag;em.UV.100-200nmfloatnullablee_F170W? Error in F170Wmagmagstat.errorfloatnullableF225W? HST/WFPC2 F225W band Vega magnitude (2)magphot.mag;em.UV.200-300nmfloatnullablee_F225W? Error in F225Wmagmagstat.errorfloatnullableF336W? HST/WFPC2 F336W band Vega magnitude (2)magphot.mag;em.opt.Ufloatnullablee_F336W? Error in F336Wmagmagstat.errorfloatnullableF439W? HST/WFPC2 F439W band Vega magnitude (2)magphot.mag;em.opt.Bfloatnullablee_F439W? Error in F439Wmagmagstat.errorfloatnullableF555W? HST/WFPC2 F555W band Vega magnitude (2)magphot.mag;em.opt.Vfloatnullablee_F555W? Error in F555Wmagmagstat.errorfloatnullableF814W? HST/WFPC2 F814W band Vega magnitude (2)magphot.mag;em.opt.Ifloatnullablee_F814W? Error in F814Wmagmagstat.errorfloatnullableUmag? The U band Vega magnitude (2)magphot.mag;em.opt.UfloatnullableBmag? The B band Vega magnitude (2)magphot.mag;em.opt.BfloatnullableVmag? The V band Vega magnitude (2)magphot.mag;em.opt.VfloatnullableImag? The I band Vega magnitude (2)magphot.mag;em.opt.IfloatnullableSharpSharpness parameter of HSTphotstat.fit.paramfloatTp[1/5] HSTphot type of the source (1=good star, 2, 4 or 5) (3)src.class.starGalaxyintFrThe visit/field from Table 1obs.fieldcharCh[0/3] WFPC2 detector (0=PC, 1=WF2, 2=WP3, 3=WF4)meta.noteint