J/A+A/670/A177ivo://CDS.VizieR/J/A+A/670/A177doi:10.26093/cds/vizier.36700177CDSFerrer Asensio J.Spezzano S.Coudert L.H.Lattanzi V.Endres C.P.,Jorgensen J.K.Caselli P.2024-11-28T20:02:04Z2023-02-24T08:06:19ZCDS support team

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

cds-question@unistra.frThe abundances of deuterated molecules with respect to their main isotopologue counterparts have been determined to be orders of magnitude higher than expected from the cosmic abundance of deuterium relative to hydrogen. The increasing number of singly and multi-deuterated species detections helps us to constrain the interplay between gas-phase and solid-state chemistry and to understand better deuterium fractionation in the early stages of star formation. Acetaldehyde is one of the most abundant complex organic molecules (COMs) in star-forming regions and its singly deuterated isotopologues have already been observed towards protostars. A spectroscopic catalogue for astrophysical purposes is built for doubly deuterated acetaldehyde (CHD_2_CHO) from measurements in the laboratory. With this accurate catalogue we aim to search and detect this species in the interstellar medium and retrieve its column density and abundance. Submillimetre wave transitions were measured for the non-rigid doubly deuterated acetaldehyde CHD_2_CHO displaying hindered internal rotation of its asymmetrical CHD_2_ methyl group. An analysis of a dataset consisting of previously measured microwave transitions and of the newly measured ones was carried out with an effective Hamiltonian which accounts for the tunneling of the asymmetrical methyl group. A line position analysis is carried out allowing us to reproduce 853 transition frequencies with a weighted root mean square standard deviation of 1.7, varying 40 spectroscopic constants. A spectroscopic catalogue for astrophysical purposes is built from the analysis results. Using this catalogue we were able to detect for the first time CHD_2_CHO towards the low-mass protostellar system IRAS 16293-2422 utilizing data from the ALMA Protostellar Interferometric Line Survey. The first detection of the CHD_2_CHO species allows for the derivation of its column density with a value of 1.3x10^15^cm^-2^ and an uncertainty of 10-20%. The resulting D_2_/D ratio of ~20% is found to be coincident with D_2_/D ratios derived for other complex organic molecules towards IRAS 16293-2422, pointing at a common formation environment with enhanced deuterium fractionation.2023A&A...670A.177Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/670/A177CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/670/A177https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/670/A177http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/670/A177https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/670/A177https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/670/A177http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/670/A177GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/670/A177/table3Line assignmentsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJuQuantum number J of the upper statephys.atmol.configurationintKauQuantum number Ka of the upper statephys.atmol.qnintKcuQuantum number Kc of the upper statephys.atmol.qnintvu[+-2] Vibrational quantum number of the upper state (1)phys.atmol.qncharJQuantum number J of the lower statephys.atmol.configurationintKaQuantum number Ka of the lower statephys.atmol.qnintKcQuantum number Kc of the lower statephys.atmol.qnintv[+-2] Vibrational quantum number of the lower state (1)phys.atmol.qncharFreqLine frequency observedMHzem.freq;spect.linedoublee_FreqLine frequency uncertaintyMHzstat.errorintO-CFrequency difference (obs - calc)MHzstat.fit.residualintn_O-C[d] Note on O-Cmeta.notecharRefReference (2)meta.ref;pos.framecharJ/A+A/670/A177/table6CHD_2_CHO spectroscopic cataloguerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFreqTransition frequencyMHzem.freq;phys.atmol.transitiondoublee_FreqTransition frequency errorMHzstat.errorfloatlogIntBase 10 logarithm of the line intensitylog(nm**2.MHz)spect.line.intensityfloatDF[3] Degrees of freedom of Q(rot)stat.fit.dofintGupUpper state degeneracyphys.electron.degenintElowLower state energycm**-1phys.energydoubleTagSpecies tagmeta.notecharQN[0/2] Format numberphys.atmol.qnintQNupUpper state quantum numbersphys.atmol.qncharQNlow[0/2] Lower state quantum numbersphys.atmol.qnint