J/AJ/158/192ivo://CDS.VizieR/J/AJ/158/192doi:10.26093/cds/vizier.51580192CDSLeitherer C.Lee J.C.Faisst A.2020-03-02T10:45:12Z2020-01-20T13:46:08ZCDS support team

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

cds-question@unistra.frmilky-way-galaxymagellanic-cloudswolf-rayet-starsinterstellar-mediumstellar-spectral-typesline-intensitiesspectroscopyultraviolet-astronomyvisible-astronomyinterstellar-reddeningWe calibrated a technique to measure dust attenuation in star-forming galaxies. The technique utilizes the stellar-wind lines in Wolf-Rayet stars, which are widely observed in galaxy spectra. The He II 1640 and 4686 features are recombination lines whose ratio is largely determined by atomic physics. Therefore they can serve as a stellar dust probe in the same way as the Balmer lines are used as a nebular probe. We measured the strength of the He II 1640 line in 97 Wolf-Rayet stars in the Galaxy and the Large Magellanic Cloud. The reddening corrected fluxes follow a tight correlation with a fixed ratio of 7.76 for the He II 1640 to 4686 line ratio. Dust attenuation decreases this ratio. We provide a relation between the stellar E(B-V) and the observed line ratio for several attenuation laws. Combining this technique with the use of the nebular Balmer decrement allows the determination of the stellar and nebular dust attenuation in galaxies and can probe its effects at different stellar age and mass regimes, independently of the initial mass function and the star formation history. We derived the dust reddening from the He II line fluxes and compared it to the reddening from the Balmer decrement and from the slope of the ultraviolet continuum in two star-forming galaxies. The three methods result in dust attenuations which agree to within the errors. Future application of this technique permits studies of the stellar dust attenuation compared to the nebular attenuation in a representative galaxy sample.2019AJ....158..192Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/158/192CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIII/143 : Spectrophotometry of Wolf-Rayet Stars (Torres-Dodgen+ 1988)III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)J/A+AS/108/669 : IUE spectra of WR stars (Niedzielski+, 1994)J/A+A/565/A27 : Wolf-Rayet stars in Large Magellanic Cloud (Hainich+, 2014)J/MNRAS/452/2858 : NIR spectroscopy of Galactic WR stars. III (Kanarek+, 2015)J/ApJ/863/181 : The fifth catalog of LMC Wolf-Rayet stars (Neugent+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/158/192https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/158/192http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/158/192https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/158/192https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/158/192http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/158/192GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/158/192/stars (Milky Way (table 1) and LMC (table 2) program stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/158/192/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/158/192/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/158/192/stars?GETtext/xml+votable180.050000true10.868333364.75983330.0055555555555555565/8274 6/3029 3616 3723 12942 14254 14255 14259 14302 14309 14315 14411 14619 14630 14631 14641 14649 15506 15622 20764 21550 28916 29097 30231 33052 33053 33075 33076 33077 33078 33094 33100 33101 33102 33107 33112 33113 33115 33120 33122 33123 33126 37232 37333 37343 37364 37370 37870 37924 37931 37936 38016 39755 39774 41419 41577 41586 41675 42163 42405 42435 43024 43042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/158/192?format=asciiUVOpticaldefaultJ/AJ/158/192/starsMilky Way (table 1) and LMC (table 2) program starsGalaxyGalaxy namemeta.id.parentcharSpTypeSpectral type (1)src.spTypecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWRW-R identifier (WR NNN or WR NNa) (1)meta.id;meta.maincharONameAlternative designationmeta.idcharRAJ2000Hour of Right Ascension (J2000) (2)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000) (2)pos.eq.dec;meta.mainIUEIdentifier of the IUE spectrum (SWPNNNNN)meta.idcharlog(EW(1640))[0.28/2.16] Measured equivalent width of He II 1640 ({AA})log(0.1nm)spect.line.eqWidthfloatlog(F(1640))[-12.89/-7.78] Measured line flux of He II 1640 (in erg/s/cm^2^)log(mW.m**-2)phot.flux;spect.linefloatCatDisplay data from the 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001, Cat. III/215)meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/AJ/158/192/table3Optical data for all program starsRef(4686)Reference for the 4686 data (1)meta.bibcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWRW-R identifier from van der Hucht (2001, Cat. III/215) or Breysacher et al. (1999A&AS..137..117B)meta.id;meta.maincharlog(EW(4686))[-0.3/2.69] Published equivalent width of He II 4686 ({AA})log(0.1nm)meta.ref;spect.line.eqWidthfloatlog(F(4686))[-12.85/-8.68]? Published line flux of He II 4686 (in erg/s/cm^2^)log(mW.m**-2)meta.ref;phot.flux;spect.linefloatnullablevmag[6.44/16.22] Published v magnitudemagphot.mag;em.opt.Vfloat(b-v)[-0.25/0.93] Published (b-v) colormagphot.color;em.opt.B;em.opt.Vfloatr_(b-v)[12/14] Reference for (b-v) (2)meta.ref;pos.frameintlog(Fc(4686))[-13.38/-8.59] Calculated line flux of He II 4686 (in erg/s/cm^2^)log(mW.m**-2)phot.flux;spect.line;meta.modelledfloatJ/AJ/158/192/table4Reddening-free He II line fluxesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWRW-R identifier from van der Hucht (2001, Cat. III/215) or Breysacher et al. (1999A&AS..137..117B)meta.id;meta.maincharE(b-v)[0.06/1.22] Published reddening from continuum fittingmagphot.color.excessfloatr_E(b-v)[1/4] Reference for the reddening data (1)meta.ref;pos.frameintlog(F0(1640))[-12.54/-7.3] Dereddened He II 1640 line flux (in erg/s/cm^2^)log(mW.m**-2)phot.flux;spect.linefloatlog(F0(4686))[-12.88/-8.06] Dereddened He II 4686 line flux (in erg/s/cm^2^)log(mW.m**-2)phot.flux;spect.linefloatlogR0[0.24/2.16] Logarithmic ratio of the 1640/4686 fluxphot.flux;arith.ratiofloat