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Search for H₃⁺ isotopologues toward CRL 2136 IRS 1

Goto, Miwa and Geballe, Thomas R. and Harju, Jorma and Caselli, Paola and Sipilä, Olli and Menten, Karl M. and Usuda, Tomonori (2019) Search for H₃⁺ isotopologues toward CRL 2136 IRS 1. Astronomy and Astrophysics, 632 . Art. No. A29. ISSN 0004-6361.

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Context. Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. H₃⁺ and its isotopologues play a key role in the deuterium fractionation; however, the abundances of these isotopologues have not been measured empirically with respect to H₃⁺ to date. Aims. Our aim was to constrain the relative abundances of H₂D⁺ and D₃⁺ in the cold outer envelope of the hot core CRL 2136 IRS 1. Methods. We carried out three observations targeting H₃⁺ and its isotopologues using the spectrographs CRIRES at the VLT, iSHELL at IRTF, and EXES on board SOFIA. In addition, the CO overtone band at 2.3 μm was observed by iSHELL to characterize the gas on the line of sight. Results. The H₃⁺ ion was detected toward CRL 2136 IRS 1 as in previous observations. Spectroscopy of lines of H₂D⁺ and D₃⁺ resulted in non-detections. The 3σ upper limits of N(H₂D⁺)/N(H₃⁺) and N(D₃⁺)/N(H₃⁺) are 0.24 and 0.13, respectively. The population diagram for CO is reproduced by two components of warm gas with the temperatures 58 and 530 K, assuming a local thermodynamic equilibrium (LTE) distribution of the rotational levels. Cold gas (<20 K) makes only a minor contribution to the CO molecular column toward CRL 2136 IRS 1. Conclusions. The critical conditions for deuterium fractionation in a dense cloud are low temperature and CO depletion. Given the revised cloud properties, it is no surprise that H₃⁺ isotopologues are not detected toward CRL 2136 IRS 1. The result is consistent with our current understanding of how deuterium fractionation proceeds.

Item Type:Article
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URLURL TypeDescription Paper
Caselli, Paola0000-0003-1481-7911
Menten, Karl M.0000-0001-6459-0669
Additional Information:© ESO 2019. Received: 17 June 2019 Accepted: 31 August 2019. Based on data collected in CRIRES DDT program [289.C-5042] at the VLT on Cerro Paranal (Chile), which is operated by the European Southern Observatory (ESO). Based on data collected by iSHELL at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. Based on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. M.G. thanks the staff and crew of the IRTF, in particular, Mike Connelley, Brian Cabreira, and Adwin Boogert. Mike Cushing and Adwin Boogert helped tremendously in the data reduction using xspextool adapted to iSHELL. M.G. also thanks Elena Valenti and Francesca Primas who helped to conduct the observation in a timely manner by CRIRES at the VLT in Director’s Discretionary Time. The authors appreciate the hospitality of the Hawaiian and Chilean communities that made the research presented here possible. M.G. thanks to Curtis DeWitt, Mat Richter and Adwin Boogert of the EXES instrumentation team who conducted actual observations from the aircraft, and delivered the reduced data to the SOFIA Data Cycle System. M.G. thanks to the anonymous reviewer for the constructive feedback. This research has made use of NASA’s Astrophysics Data System. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. M.G. is supported by the German Research Foundation (DFG) grant GO 1927/6-1. T.R.G.’s research is supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).
Group:Thirty Meter Telescope
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)GO 1927/6-1
Gemini ObservatoryUNSPECIFIED
Subject Keywords:astrochemistry / ISM: molecules / ISM: clouds / stars: individual: CRL 2136 IRS 1 / ISM: lines and bands / infrared: ISM
Record Number:CaltechAUTHORS:20200316-150528746
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Official Citation:Search for H3+ isotopologues toward CRL 2136 IRS 1 Miwa Goto, Thomas R. Geballe, Jorma Harju, Paola Caselli, Olli Sipilä, Karl M. Menten and Tomonori Usuda A&A, 632 (2019) A29 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101929
Deposited By: George Porter
Deposited On:17 Mar 2020 14:54
Last Modified:17 Mar 2020 14:54

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