J/A+A/620/A52ivo://CDS.VizieR/J/A+A/620/A52doi:10.26093/cds/vizier.36200052CDSRamirez-Tannus M.C.Cox N.L.J.Kaper L.de Koter A.2019-11-11T22:00:00Z2018-11-29T08:04:21ZCDS support team

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

cds-question@unistra.frstar-forming-regionspre-main-sequence-starsyoung-stellar-objectsob-starsinterstellar-mediumDiffuse interstellar bands (DIBs) are broad absorption features measured in sightlines probing the diffuse interstellar medium. Although large carbon-bearing molecules have been proposed as the carriers producing DIBs, their identity remains unknown. DIBs make an important contribution to the extinction curve; the sightline. to the young massive star-forming region M17 shows anomalous extinction in the sense that the total-to-selective extinction parameter (R_V_) differs significantly from the average Galactic value and may reach values R_V_>4. Anomalous DIBs have been reported in the sightline towards Herschel 36 (R_V_=5.5), in the massive star-forming region M8. Higher values of R_V_ have been associated with a relatively higher fraction of large dust grains in the line of sight. Given the high R_V_ values, we investigate whether the DIBs in sightlines towards young OB stars in M17 show a peculiar behaviour. We measure the properties of the most prominent DIBs in M17 and study these as a function of E(B-V) and R_V_. We also analyse the gaseous and dust components contributing to the interstellar extinction. The DIB strengths in M17 concur with the observed relations between DIB equivalent width and reddening E(B-V) in Galactic sightlines. For several DIBs we discover a linear relation between the normalised DIB strength EW/A_V_ and R_V_^-1^. These trends suggest two groups of DIBs: (i) a group of ten moderately strong DIBs that show a sensitivity to changes in R_V_ that is modest and proportional to DIB strength, and (ii) a group of four very strong DIBs that react sensitively and to a similar degree to changes in R_V_, but in a way that does not appear to depend on DIB strength. DIB behaviour as a function of reddening is not peculiar in sightlines to M17. Also, we do not detect anomalous DIB profiles like those seen in Herschel 36. DIBs are stronger, per unit visual extinction, in sightlines characterised by a lower value of R_V_, i.e. those sightlines that contain a relatively large fraction of small dust particles. New relations between extinction normalised DIB strengths, EW/A_V_, and R_V_ support the idea that DIB carriers and interstellar dust are intimately connected. Furthermore, given the distinct behaviour of two groups of DIBs, different types of carriers do not necessarily relate to the dust grains in a similar way.2018A&A...620A..52Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/620/A52CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/604/A78 : M17 massive pms stars X-shooter spectra (Ramirez-Tannus+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/620/A52https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/620/A52http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/620/A52https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/620/A52https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/620/A52http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/620/A52GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/620/A52/table1 (Extinction properties measured in the sight lines towards M17)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A52/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A52/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A52/table1?GETtext/xml+votable180.050000true275.1437106-16.16995580.0055555555555555566/29116 29118https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/620/A52?format=asciidefaultJ/A+A/620/A52/table3DIB EW and FWHM towards M17 sightlinesIdIdentifier, BNNNmeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaCentral wavelength of DIB0.1nmem.wl.centralintFWHM? Full width at half maximumnmspect.line.widthfloatnullableEW? Equivalent width0.1pmspect.line.eqWidthintnullablee_EW? Error on the measurement of EW0.1pmstat.error;spect.line.eqWidthintnullableJ/A+A/620/A52/table1Extinction properties measured in the sight lines towards M17recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFWHM/EWDisplay the FWHM/EW datameta.ref.urlcharIdIdentifier, BNNN (Cl* NGC 6618 B NNN in Simbad)meta.id;meta.maincharSpTypeSpectral type from Paper Isrc.spTypecharBmag? B magnitudemagphot.mag;em.opt.Bfloatnullabler_Bmag[bcd] Reference for B mag (1)meta.ref;pos.framecharVmag? V magnitudemagphot.mag;em.opt.Vfloatnullabler_Vmag[bcd] Reference for Vmag (1)meta.ref;pos.framecharKmag2MASS (Cat. II/246) K magnitudemagphot.mag;em.IR.KfloatRvSEDTotal-to-selective visual extinction R_V_ derived by fitting the spectral energy distribution to Kurucz modelsmagphys.absorptionfloatE_RvSED? Error on RvSED (upper value)magstat.error;stat.maxfloatnullablee_RvSEDError on RvSED (lower value)magstat.errorfloatRVFitzp? Total-to-selective visual extinction R_V_ derived using Eq (1) (see Sect. 3)magphys.absorptionfloatnullableAVSEDV-band colour excess A_V_ derived by fitting the spectral energy distribution to Kurucz modelsmagphot.color.excessfloatE_AVSED? Error on AVSED (upper value)magstat.error;stat.maxfloatnullablee_AVSEDError on AVSED (lower value)magstat.errorfloatAV? V-band colour excess A_V_ (2)magphot.color.excessfloatnullableE(B-V)SEDExtinction parameter E(B-V)=AV/Rv derived by fitting the spectral energy distribution to Kurucz modelsmagphot.color.excessfloate_E(B-V)SEDrms uncertainty on E(B-V)SEDmagstat.errorfloatE(B-V)? Colour excess (B-V)-(B-V)0 (2)magphot.color.excessfloatnullableAK? Extinction parameter A_K_ derived using Eq (1) (see Sect. 3)magphot.color.excessfloatnullablePapDisplay the Paper I (Cat. J/A+A/604/A78) datameta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main