J/A+A/633/A120ivo://CDS.VizieR/J/A+A/633/A120doi:10.26093/cds/vizier.36330120CDSGiesen T.F.Mookerjea B.Fuchs G.W.Breier A.A.Witsch D.Simon R.,Stutzki J.2020-04-27T13:22:39Z2020-01-21T07:26:20ZCDS support team

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

cds-question@unistra.frstar-forming-regionsinterstellar-mediumspectroscopyCarbon molecules and their ^13^C-isotopologues can be used to determine the ^12^C/^13^C abundance ratios in stellar and interstellar objects. C3 is a pure carbon chain molecule found in star forming regions and in stellar shells of carbon-rich late-type stars. Latest laboratory data of ^13^C-isotopologues of C3 allow a selective search for the mono-substituted species ^13^CCC and C^13^CC based on accurate ro-vibrational frequencies. Our aim was to provide the first detection of the ^13^C-isotopologues ^13CCC and C^13^CC in space and to derive the ^12^C/ ^13^C ratio of interstellar gas in the massive star-forming region SgrB2(M) near the Galactic Center. We used the heterodyne receivers GREAT and upGREAT on board SOFIA to search for the ro-vibrational transitions Q(2) and Q(4) of ^13^CCC and C^13^CC at 1.9THz along the line of sight towards SgrB2(M). In addition, to determine the local excitation temperature we analyzed data from nine ro-vibrational transitions of the main isotopologue CCC in the frequency range between 1.6-1.9THz which were taken from the Herschel Science Data Archive. We report the first detection of the isotopologues ^13^CCC and C^13^CC. For both species the ro-vibrational absorption lines Q(2) and Q(4) have been identified, primarily arising from the warm gas physically associated with the strong continuum source SgrB2(M). From the available CCC ro-vibrational transitions we derived a gas excitation temperature of Tex=44.4^+4.7^_-3.9_K and a total column density of N(CCC)=3.88^+0.39^_-0.35_x10^15^cm^-2.. Assuming the excitation temperatures of C^13^CC and ^13^CCC to be the same as for CCC, we obtained column densities of the ^13^C-isotopologues of N(C^13^CC)=2.1^+0.9^_-0.6^_x10^14^cm^-2^ and N(^13^CCC)=2.4^+1.2^_-0.8_x10^14^cm^-2^. The derived ^12^C/^13^C abundance ratio in the C3 molecules is 20.5+/-4.2, which is in agreement with the elemental ratio of 20, typically observed in SgrB2(M). However, we find the N(^13^CCC)/N(C^13^CC) ratio to be 1.2+/-0.1, which is shifted from the statistically expected value of 2. We propose that the discrepant abundance ratio arises due to the the lower zero-point energy of C^13^CC which makes position- exchange reaction converting C^13^CC to C^13^CC energetically favorable.2020A&A...633A.120Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/633/A120CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/559/A47 : Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/633/A120https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/633/A120http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/633/A120https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/633/A120https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/633/A120http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/633/A120GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/633/A120/list (List of fits spectra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/633/A120/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/633/A120/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/633/A120/list?GETtext/xml+votable180.050000true266.83479-28.384170.0055555555555555566/28830https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/633/A120?format=asciidefaultJ/A+A/633/A120/listList of fits spectraspShow the spectrummeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablebFREQLower value of frequency intervalHzem.freqdoubleBFREQUpper value of frequency intervalHzem.freqdoubledFREQFrequency resolutionHzspect.resolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar