Jaber, A. A.
Lepine, J. R. D.
Boechat-Roberty, H. M.
Total Authors: 13
 Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo, SP - Brazil
 Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble - France
 Univ AL Muthanna, Coll Sci, Phys Dept, Al Muthanna - Iraq
 Ist Astrofis & Planetol Spaziali, INAF, Via Fosso Cavaliere 100, I-00133 Rome - Italy
 UCL, Dept Phys & Astron, Gower St, London WC1E 6BT - England
 Queen Mary Univ London, Sch Phys & Astron, Mile End Rd, London E1 4NS - England
 Univ Fed Rio de Janeiro, Observ Valongo, BR-20080090 Rio de Janeiro, RJ - Brazil
 Observ Astron Nacl, IGN, Calle Alfonso XII, E-28004 Madrid - Spain
Total Affiliations: 9
Monthly Notices of the Royal Astronomical Society;
Web of Science Citations:
We present here a systematic search for cyanopolyynes in the shock region L1157-B1 and its associated protostar L1157-mm in the framework of the Large Program `Astrochemical Surveys At IRAM' (ASAI), dedicated to chemical surveys of solar-type star-forming regions with the IRAM 30-m telescope. Observations of the millimeter windows between 72 and 272 GHz permitted the detection of HC3N and its 13C isotopologues, and HC5N (for the first time in a protostellar shock region). In the shock, the analysis of the line profiles shows that the emission arises from the outflow cavities associated with L1157-B1 and L1157-B2. Molecular abundances and excitation conditions were obtained from the analysis of the Spectral Line Energy Distributions under the assumption of Local Thermodynamical Equilibrium or using a radiative transfer code in the Large Velocity Gradient approximation. Towards L1157 mm, the HC3N emission arises from the cold envelope (T-rot = 10 K) and a higher-excitation region (T-rot = 31 K) of smaller extent around the protostar. We did not find any evidence of C-13 or D fractionation enrichment towards L1157-B1. We obtain a relative abundance ratio HC3N/HC5N of 3.3 in the shocked gas. We find an increase by a factor of 30 of the HC3N abundance between the envelope of L1157-mm and the shock region itself. Altogether, these results are consistent with a scenario in which the bulk of HC3N was produced by means of gas phase reactions in the passage of the shock. This scenario is supported by the predictions of a parametric shock code coupled with the chemical model UCL\_CHEM. (AU)