J/A+A/657/A96ivo://CDS.VizieR/J/A+A/657/A96doi:10.26093/cds/vizier.36570096CDSAgundez M.Marcelino N.Cabezas C.Fuentetaja R.Tercero B.,de Vicente P.Cernicharo J.2022-03-21T09:30:15Z2022-01-17T07:52:09ZCDS support team

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

cds-question@unistra.fratomic-physicsWe report the detection of the propargyl radical (CH_2_CCH) in the cold dark cloud TMC-1 in the lambda 3mm wavelength band. We recently discovered this species in space toward the same source at a wavelength of lambda 8mm. In those observations, various hyperfine components of the 202-101 rotational transition, at 37.5GHz, were detected using the Yebes 40m telescope. Here, we used the IRAM 30m telescope to detect ten hyperfine components of the 505-404 rotational transition, lying at 93.6GHz. The observed frequencies differ by 0.2MHz with respect to the predictions from available laboratory data. This difference is significant for a radioastronomical search for CH_2_CCH in interstellar sources with narrow lines. We thus included the measured frequencies in a new spectroscopic analysis to provide accurate frequency predictions for the interstellar search for propargyl at mm wavelengths. Moreover, we recommend that future searches for CH_2_CCH in cold interstellar clouds are carried out at lambda 3mm, rather than at lambda 8 mm. The 505-404 transition is about five times more intense than the 202-101 transition in TMC-1, which implies that detecting the former requires about seven times less telescope time than detecting the latter. We constrain the rotational temperature of CH_2_CCH in TMC-1 to 9.9+/-1.5K, which indicates that the rotational levels of this species are thermalized at the gas kinetic temperature. The revised value of the column density of CH_2_CCH (including ortho and para species) is (1.0+/-0.2)x10^14^cm^-2^, and thus the CH_2_CCH/CH_3_CCH abundance ratio is revised from slightly below one to nearly one. This study opens the door for future detections of CH_2_CCH in other cold interstellar clouds, making possible to further investigate the role of this very abundant hydrocarbon radical in the synthesis of large organic molecules such as aromatic rings.2022A&A...657A..96Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/657/A96CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/657/A96https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/657/A96http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/657/A96https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/657/A96https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/657/A96http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/657/A96GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/657/A96/tablea1Predicted frequencies for CH_2_CCH at 300KrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFreqCalculated transition frequencyMHzem.freq;phys.atmol.transition;meta.modelleddoubleO-CUncertainty of calculated transition frequencyMHzstat.error;em.freq;stat.fit.omcfloatlogIntBase 10 logarithm of the integrated intensitylog(nm**2.MHz)spect.line.intensityfloatDOFDegrees of freedom in the partition functionstat.fit.dofintElowEnergy of the lower statecm**-1phys.energydoublegupUpper state degeneracyphys.electron.degenintTagSpecies tag or molecular identifiermeta.id;phys.molintQNFMTIdentifies the format of the quantum numbers given in the field QNphys.mol.qncharQNQuantum numbers coded according to QNFMTphys.mol.qnchar