J/ApJ/812/L5ivo://CDS.VizieR/J/ApJ/812/L5doi:10.26093/cds/vizier.18129005CDSHalfen D.T.Ilyushin V.V.Ziurys L.M.2017-01-23T22:00:00Z2016-03-11T15:02:01ZCDS support team

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

cds-question@unistra.fratomic-physicsinterstellar-mediumradio-spectroscopyA new interstellar molecule, CH_3_NCO (methyl isocyanate), has been detected using the 12m telescope of the Arizona Radio Observatory (ARO). CH_3_NCO was identified in spectra covering 48GHz (68-116GHz) in the 3mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (K_a_=0 and K_a_=1 only; E_u_<60K) originating in five consecutive transitions (J=8->7, 9->8, 10->9, 11->10, and 12->11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with T_R_^*^~20-70mK. The CH_3_NCO spectra also appear to exhibit two velocity components near V_LSR_~62 and 73km/s, both with {Delta}V_1/2_~10km/s --typical of molecules such as CH_2_CHCN, HNCO, and HCOOCH_3_ in Sgr B2(N). The column density of CH_3_NCO in Sgr B2(N) was determined to be N_tot_~2.3x10^13^ and 1.5x10^13^/cm^2^ for the 62 and 73km/s components, corresponding to fractional abundances, relative to H_2_, of f~7.6x10^-12^ and 5.0x10^-12^, respectively. CH_3_NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ~1.3% of water; in Sgr B2(N), CH_3_NCO is roughly ~0.04% of the H_2_O abundance.2015ApJ...812L...5Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/812/L5CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/566/L5 : C/2012 F6 (Lemmon) & C/2013 R1 spectra (Lovejoy) (Biver+, 2014)J/A+A/559/A47 : Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013)J/ApJ/724/994 : Cyano- to methanol and ammonia observations (Braakman+, 2010)J/A+A/455/971 : Organic molecules in Galactic center (Requena-Torres+, 2006)J/ApJS/158/188 : Detection of glycolaldehyde toward Sgr B2 (Widicus+, 2005)J/ApJS/117/427 : Sgr B2 spectral survey (Nummelin+, 1998)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/812/L5https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/812/L5http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/812/L5https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/812/L5https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/812/L5http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/812/L5GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/812/L5/table1Previous and new rest frequencies of CH_3_NCO (vb=0) of the revised analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJ1[1/12] Upper J quantum numberinstr.det.qe;stat.maxintKa1[-3/3] Upper Ka quantum numberphys.atmol.qn;stat.maxintKc1[1/12] Upper Kc quantum numberphys.atmol.qn;stat.maxintJ0[0/11] Lower J quantum numberinstr.det.qe;stat.minintKa0[-3/3] Lower Ka quantum numberphys.atmol.qn;stat.minintKc0[0/11] Lower Kc quantum numberphys.atmol.qn;stat.minintA/E[AE] A/E symmetryphys.atmol.paritycharm[-3/4] Internal rotation quantum number, mphys.atmol.qnintFreq[8671.3/104999] Frequency of the transitionMHzem.freq;phys.atmol.transitiondoubleO-C[-2/1.3] Observed minus calculated valueMHzstat.fit.residualfloatr_Freq[ab] Source of frequency (1)meta.ref;pos.framecharJ/ApJ/812/L5/table3Observed parameters for CH_3_NCO in Sgr B2(N)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTransTransition J'_Ka,Kc_->J"_Ka,Kc_phys.atmol.transProb;phys.atmol.transitionA/E[AE] A/E symmetryphys.atmol.paritycharm[0/1]? Internal rotation quantum number, mphys.atmol.qnintnullableFreq[68536.7/105000.3]? Frequency of the transitionMHzem.freq;phys.atmol.transitiondoublenullablee_Freq[0.005/1.2]? Freq uncertaintyMHzstat.errorfloatnullableEu[14.9/57.5]? Upper state energyKphys.energy;phys.atmol.levelfloatnullablemu2S[63/98.6]? Line strength ({mu}^2^S)D**2spect.line.intensityfloatnullableetac[0.8/1]? Corrected beam efficiency {eta}_c_stat.fit.paramfloatnullabletheta[60/92]? {theta}_b_ valuearcsecphys.angSizeintnullablel_TR*[~] Uncertainty flag on TR*meta.code.errorcharTR*[0.01/0.08]? Temperature scale (1)Kphys.temperaturefloatnullablee_TR*[0.002/0.005]? TR* uncertaintyKstat.errorfloatnullablel_DelV12[~] Uncertainty flag on DelV12meta.code.errorcharDelV12[10/22]? Difference between the two velocity components ({Delta}V_1/2_)km/sphys.veloc;arith.diffintnullablee_DelV12[2/4]? DelV12 uncertaintykm/sstat.errorintnullableu_Vlsr[~] Uncertainty flag on Vlsrmeta.code.error;phys.veloc;pos.lsrcharVlsr[62/73]? LSR velocitykm/sphys.veloc;pos.lsrintnullablee_Vlsr[2/4]? Vlsr uncertaintykm/sstat.error;phys.veloc;pos.lsrintnullablef_Vlsr[a] Flag on Vlsrmeta.codecharCommCommentmeta.note