High-spatial-resolution CN and CS observation of two regions of massive star formation

Molecular line CN, CS and mm continuum observations of two intermediate- to high-mass star-forming regions - IRAS20293+3952 and IRAS19410+2336 - obtained with the Plateau de Bure Interferometer at high spatial resolution reveal interesting characteristics

DraftfromFebruary2,2008,toappearinApJ

High-spatial-resolutionCNandCSobservationoftworegionsof

massivestarformation

H.Beuther

arXiv:astro-ph/0407384v1 19 Jul 2004Harvard-SmithsonianCenterforAstrophysics,60GardenStreet,Cambridge,MA02138hbeuther@cfa.harvard.eduP.Schilke,F.WyrowskiMax-Planck-InstituteforRadioastronomy,AufdemH¨ugel69,53121Bonn,GermanyABSTRACTMolecularlineCN,CSandmmcontinuumobservationsoftwointermediate-tohigh-massstar-formingregions–IRAS20293+3952andIRAS19410+2336–obtainedwiththePlateaudeBureInterferometerathighspatialresolutionrevealinterestingcharacteristicsofthegasanddustemission.InspiteoftheexpectationthattheCNandCSmorphologymightcloselyfollowthedensegastracedbythedustcontinuum,bothmoleculesavoidthemostcentralcores.ComparingtherelativelinestrengthsofvariousCNhyper necomponents,thisappearsnottobeanopacitye ectbuttobeduetochemicalandphysicale ects.TheCNdataalsoindicateenhancedemissiontowardthedi erentmolecularout owsintheregion.RegardingCS,avoidingthecentralcorescanbeduetohighoptical

depth,butthedataalsoshowthattheCSemissionisnearlyalwaysassociated

withtheout owsoftheregion.Therefore,neitherCSnorCNappearwellsuited

fordensegasanddiskstudiesinthesetwosources,andwerecommendtheuseof

di erentmoleculesforfuturemassivediskstudies.Ananalysisofthe1and3mm

continuum uxestowardIRAS20293+3952revealsthatthedustopacityindex

βislowerthanthecanonicalvalueof2.Tentatively,weidentifyadecreasing

gradientofβfromtheedgeofthecoretothecorecenter.Thiscouldbedueto

increasingopticaldepthtowardthecorecenterand/orgraingrowthwithinthe

densestcoresandpotentialcentraldisks.Wedetect3mmcontinuumemission

towardthecollimatedout owemanatingfromIRAS20293+3952.Thespectral

indexofα～0.8inthisregionisconsistentwithstandardmodelsforcollimated

ionizedwinds.

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