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Published July 2010 | Published
Journal Article Open

The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1: I. Shock chemical complexity

Abstract

We present the first results of the unbiased survey of the L1157-B1 bow shock, obtained with HIFI in the framework of the key program Chemical HErschel Survey of Star forming regions (CHESS). 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 bright blue-shifted bow shock B1 is the ideal laboratory for studying the link between the hot (~1000–2000 K) component traced by H_2 IR-emission and the cold (~10–20 K) swept-up material. The main aim is to trace the warm gas chemically enriched by the passage of a shock and to infer the excitation conditions in L1157-B1. A total of 27 lines are identified in the 555–636 GHz region, down to an average 3σ level of 30 mK. The emission is dominated by CO(5–4) and H_(2)O(1_(10)–1_(01)) transitions, as discussed by Lefloch et al. in this volume. Here we report on the identification of lines from NH_3, H_(2)CO, CH_(3)OH, CS, HCN, and HCO^+. The comparison between the profiles produced by molecules released from dust mantles (NH_3, H_(2)CO, CH_(3)OH) and that of H_(2)O is consistent with a scenario in which water is also formed in the gas-phase in high-temperature regions where sputtering or grain-grain collisions are not efficient. The high excitation range of the observed tracers allows us to infer, for the first time for these species, the existence of a warm (≥200 K) gas component coexisting in the B1 bow structure with the cold and hot gas detected from ground.

Additional Information

© 2010 ESO. Received 30 March 2010; Accepted 5 May 2010. Published online 16 July 2010. Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA. Table 1 is only available in electronic form at http://www.aanda.org. 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, U. 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 thank many funding agencies for financial support.

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