J/ApJ/932/5ivo://CDS.VizieR/J/ApJ/932/5doi:10.26093/cds/vizier.19320005CDSKalenskii S.V.Kaiser R.I.Bergman P.Olofsson A.O.H.Degtyarev K.D.,Golysheva P.2025-09-22T20:10:39Z2025-05-15T09:06:42ZCDS support team

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

cds-question@unistra.frmolecular-physicsstar-forming-regionsradio-spectroscopyWe present the results of a spectral-line survey of the W51e1/e2 star-forming region at 68-88GHz. 79 molecules and their isotopologues were detected, from simple diatomic or triatomic molecules, such as SO, SiO, and CCH, to complex organic compounds, such as CH3OCH3 or CH3COCH3. A number of lines that are absent from the Lovas list of molecular lines observed in space were detected, and most of these were identified. A significant number of the detected molecules are typical for hot cores. These include the neutral molecules HCOOCH3, CH3CH2OH, and CH3COCH3, which are currently believed to exist in the gas phase only in hot cores and shock-heated gas. In addition, vibrationally excited C4H and HC3N lines with upper-level energies of several hundred Kelvins were found. Such lines can arise only in hot gas with temperatures on the order of 100K or higher. Apart from neutral molecules, various molecular ions were also detected. Some of these (HC18O+, H13CO+, and HCS+) usually exist in molecular clouds with high visual extinctions. Potential formation pathways of complex organic molecules and hydrocarbons, along with nitriles, are considered. These formation routes are first discussed in the context of laboratory experiments elucidating the synthesis of organic molecules in interstellar ices in cold molecular clouds, followed by sublimation into the gas phase in the hot core stage. Thereafter, we discuss the predominant formation of hydrocarbons and their nitriles in the gas phase through bimolecular neutral-neutral reactions.2022ApJ...932....5Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/932/5CatalogResearchIsServedByTAP VizieR generic servicerelated-toV/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002)J/ApJ/720/1055 : VBLA observations of W51 Main/South (Sato+, 2010)J/A+A/582/A64 : W51/e2 and G34.3+0.2 IRAM spectra (Lykke+, 2015)J/A+A/595/A27 : JVLA images of W51A (Ginsburg+, 2016)J/A+A/589/A44 : W51 Main NH_3_ and CH_3_OH data cubes (Goddi+, 2016)J/A+A/631/A137 : IRAS 16293-2422 CH_3_CCH spectral cubes (Calcutt+, 2019)J/ApJ/883/129 : ALMA obs. of SFRs toward NGC6334I (El-Abd+, 2019)J/ApJ/900/L10 : X-band data of GOTHAM Large Project for TMC-1 (McGuire+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/932/5https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/932/5http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/932/5https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/932/5https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/932/5http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/932/5GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/932/5/table1Gaussian parameters of detected lines for W51e1/e2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintComp[0/2] Component of blended lines (1)meta.codeintFreq[68305.68/87899.5] Rest FrequencyMHzem.freqdoubleMolMoleculemeta.id;phys.molTransTransitionmeta.id;phys.atmol.transitionTRdV[0.02/39.1]? Integrated intensity, Gaussian fitK.km/sspect.line.intensityfloatnullablee_TRdV[0.004/2.7]? Uncertainty in TRdVK.km/sstat.error;spect.line.intensityfloatnullableVLSR[43/66.4]? Radial velocity, relative to LSR, Gaussian fitkm/sspect.dopplerVeloc;pos.lsrfloatnullablee_VLSR[0/4.1]? Uncertainty in VLSRkm/sstat.error;phys.veloc;pos.lsrfloatnullabledV[3.4/44]? Linewidth, Gaussian fitkm/sspect.line.widthfloatnullablee_dV[0/7.1]? Uncertainty in dVkm/sstat.error;spect.line.widthfloatnullableTr[0.002/4.3]? Line peak temperatureKphys.temperature;spect.line.intensityfloatnullableNotesNotes (2)meta.notechar