J/ApJ/693/L81ivo://CDS.VizieR/J/ApJ/693/L81doi:10.26093/cds/vizier.16939081CDSMcClure M.2017-06-12T08:25:26Z2011-03-21T15:30:17ZCDS support team

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

cds-question@unistra.frmolecular-cloudsextinctioninfrared-sourcesdwarf-starsUsing Spitzer Infrared Spectrograph observations of G0-M4III stars behind dark clouds, I construct 5-20um empirical extinction curves for 0.3<=A_K_<7, which is equivalent to A_V_ between ~3 and 50. For A_K_<1, the curve appears similar to the Mathis diffuse interstellar medium extinction curve, but with a greater degree of extinction. For A_K_>1, the curve exhibits lower contrast between the silicate and absorption continuum, develops ice absorption, and lies closer to the Weingartner and Draine R_V_=5.5 Case B curve, a result which is consistent with that of Flaherty et al. (2007ApJ...663.1069F) and Chiar et al. (2007ApJ...666L..73C). Recently, work using Spitzer Infrared Array Camera data by Chapman et al. independently reaches a similar conclusion that the shape of the extinction curve changes as a function of increasing A_K_. By calculating the optical depths of the 9.7um silicate and 6.0, 6.8, and 15.2um ice features, I determine that a process involving ice is responsible for the changing shape of the extinction curve and speculate that this process is a coagulation of ice-mantled grains rather than ice-mantled grains alone.2009ApJ...693L..81Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/693/L81CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/663/320 : IR-through-UV extinction curve (Fitzpatrick+, 2007)J/A+AS/111/57 : Synthetic absorption in star forming regions (Olofsson, 1995)J/A+A/275/549 : Interstellar extinction curves (Jenniskens+ 1993)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/693/L81https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/693/L81http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/693/L81https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/693/L81https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/693/L81http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/693/L81GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/693/L81/table1 (Spectral type information for the entire sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/693/L81/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/693/L81/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/693/L81/table1?GETtext/xml+votable180.050000true326.841833347.57805560.0055555555555555566/1054 1063 1073 14052 14053 29193 29211 30363 30366 36953 36956https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/693/L81?format=asciiInfrareddefaultJ/ApJ/693/L81/table1Spectral type information for the entire samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCldCloud namemeta.id.parentcharNameStar namemeta.id;meta.maincharr_Name[b] Flag on Name (1)meta.ref;pos.framechar2MASSJ2MASS designation (HHMMSSss+DDMMSSs)meta.idcharSpTMK spectral typesrc.spTypecharr_SpT[c] Flag on SpT (2)meta.ref;pos.framecharPIDAOR number (Astronomical Observation Request identification number)meta.id;obsintl_AKLimit flag on AKmeta.code.errorcharAK? K-band extinction (3)phys.absorptionfloatnullablee_AK? AK uncertaintystat.errorfloatnullabletau9.7? Optical depth of the 9.7um silicatephys.absorption.opticalDepthfloatnullablee_tau9.7? tau9.7 uncertaintystat.errorfloatnullabletauH2O? Optical depth of the 6um (H_2_O ice)phys.absorption.opticalDepthfloatnullablee_tauH2O? tauH2O uncertaintystat.errorfloatnullabletauMet? Optical depth of the 6.8um ("methanol" ice)phys.absorption.opticalDepthfloatnullablee_tauMet? tauMet uncertaintystat.errorfloatnullabletauCO2? Optical depth of the 15.2um (CO_2_ ice)phys.absorption.opticalDepthfloatnullablee_tauCO2? tauCO2 uncertaintystat.errorfloatnullable2MDisplay the 2MASS data (Cutri et al. 2003, Cat. II/246)meta.ref.urlcharSimbadSimbad column added by the CDSchar_RAPositions from 2MASS name (right ascension part)degpos.eq.ra;meta.main_DEPositions from 2MASS name (declination part)degpos.eq.dec;meta.mainJ/ApJ/693/L81/table2Final, composite extinction curvesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength (1)umem.wldoubleAl/AK1A_{lambda}_/A_Ks_ for 0.3<A_k_<1phys.absorption.coeffdoubleAl/AK2A_{lambda}_/A_Ks_ for 1<A_k_<7phys.absorption.coeffdouble