A 2 mm spectral line survey of the starburst galaxy NGC 253

We present the first unbiased molecular line survey towards an extragalactic source, namely the nuclear region of the starburst galaxy NGC 253. The scan covers the frequency band from 129.1 to 175.2 GHz, i.e. most of the 2mm atmospheric window. We identify

A2mmspectrallinesurveyofthestarburstgalaxyNGC253

S.Mart´ n

InstitutodeRadioastronom´ aMilim´etrica(IRAM),Avda.DivinaPastora7,Local20,

E-18012Granada,Spain

arXiv:astro-ph/0602360v1 16 Feb 2006martin@iram.esR.MauersbergerInstitutodeRadioastronom´ aMilim´etrica(IRAM),Avda.DivinaPastora7,Local20,E-18012Granada,SpainJ.Mart´ n-PintadoDepartamentodeAstro s´ caMoleculareInfrarroja,InstitutodeEstructuradelaMateria,CSIC,Serrano121,E-28006Madrid,SpainC.HenkelMax-Planck-Institutf¨urRadioastronomie,AufdemH¨ugel69,D-53121Bonn,GermanyandS.Garc´ a-BurilloObservatoriodeMadrid,AlfonsoXII,3,28014Madrid,SpainABSTRACT

Wepresentthe rstunbiasedmolecularlinesurveytowardsanextragalac-

ticsource,namelythenuclearregionofthestarburstgalaxyNGC253.Thescancoversthefrequencybandfrom129.1to175.2GHz,i.e.mostofthe2mmatmosphericwindow.Weidentify111spectralfeaturesastransitionsfrom25dif-ferentmolecularspecies.Eightofwhich(threetentatively)aredetectedforthe rsttimeintheextragalacticinterstellarmedium.Amongthesenewlydetectedspecies,wedetectedtherareisotopomers34SOandHC18O+.Tentativedetec-tionsoftwodeuteratedspecies,DNCandN2D+,arereportedforthe rsttimefromatargetbeyondtheMagellanicClouds.Additionally,threehydrogenre-combinationlinesareidenti ed,whilenoorganicmoleculeslargerthanmethanolaredetected.Columndensitiesandrotationtemperaturesarecalculatedforall

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