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Published September 20, 2012 | Published + Erratum
Journal Article Open

The Herschel and IRAM CHESS Spectral Surveys of the Protostellar Shock L1157-B1: Fossil Deuteration

Abstract

We present the first study of deuteration toward the protostellar shock L1157-B1, based on spectral surveys performed with the Herschel-HIFI and IRAM 30 m telescopes. The L1157 outflow is driven by a low-mass Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The young (2000 yr), bright blueshifted bow shock, B1, is an ideal laboratory for studying the gas chemically enriched by the release of dust mantles due to the passage of a shock. A total of 12 emission lines (up to E_u = 63 K) of CH_(2)DOH, HDCO, and DCN are detected. In addition, two lines of NH_(2)D and HDO are tentatively reported. To estimate the deuteration, we also extracted from our spectral survey emission lines of non-deuterated isotopologues (^(13)CH_(3)OH, H_2 ^(13)CO, H^(13)CN, H_2 ^(13)CO, and NH_3). We infer higher deuteration fractions for CH_(3)OH (D/H = 0.2-2 × 10^(–2)) and H_(2)CO (5-8 × 10^(–3)) than for H_(2)O (0.4-2 × 10^(–3)), HCN (~10^(–3)), and ammonia (≤3 × 10^(–2)). The measurement of deuteration of water, formaldehyde, and methanol in L1157-B1 provides a fossil record of the gas before it was shocked by the jet driven by the protostar. A comparison with gas-grain models indicates that the gas passed through a low-density (≤10^3 cm^(–3)) phase, during which the bulk of water ices formed, followed by a phase of increasing density, up to 3 × 10^4 cm^(–3), during which formaldehyde and methanol ices formed.

Additional Information

© 2012 American Astronomical Society. Received 2012 July 2; accepted 2012 August 8; published 2012 August 31. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada, and the United States under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France, and the US. Consortium members are: Canada: CSA, University of Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronómico Nacional (IGN), Centro de Astrobiología (CSIC-INTA); Sweden: Chalmers University of Technology-MC2, RSS & GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University - Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC. We also thank many funding agencies for financial support. Support for this work was provided by NASA through an award issued by JPL/Caltech. The CSO is supported by the National Science Foundation under the contract AST-08388361. C. Codella, C. Ceccarelli, and B. Lefloch acknowledge the financial support from the COST Action CM0805 "The Chemical Cosmos" and the French spatial agency CNES. G. Busquet and M. Vasta are supported by an Italian Space Agency (ASI) fellowship under contract number I/005/007.

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Published - 2041-8205_757_1_L9.pdf

Erratum - 2041-8205_759_2_L45.pdf

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August 22, 2023
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