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Journal articles

Broad N2H+ Emission toward the Protostellar Shock L1157-B1

Abstract : We present the first detection of N2H+ toward a low-mass protostellar outflow, namely, the L1157-B1 shock, at ~0.1 pc from the protostellar cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N2H+(1-0) line originated from the dense (>=105 cm-3) gas associated with the large (20''-25'') cavities opened by the protostellar wind. We find an N2H+ column density of a few 1012 cm-2 corresponding to an abundance of (2-8) × 10-9. The N2H+ abundance can be matched by a model of quiescent gas evolved for more than 104 yr, i.e., for more than the shock kinematical age (sime2000 yr). Modeling of C-shocks confirms that the abundance of N2H+ is not increased by the passage of the shock. In summary, N2H+ is a fossil record of the pre-shock gas, formed when the density of the gas was around 104 cm-3, and then further compressed and accelerated by the shock.
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Contributor : Nathalie Pothier Connect in order to contact the contributor
Submitted on : Sunday, March 27, 2022 - 10:56:30 AM
Last modification on : Monday, March 28, 2022 - 4:10:22 AM

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C. Codella, S. Viti, C. Ceccarelli, B. Lefloch, M. Benedettini, et al.. Broad N2H+ Emission toward the Protostellar Shock L1157-B1. The Astrophysical Journal, 2013, 776, ⟨10.1088/0004-637X/776/1/52⟩. ⟨insu-03620889⟩



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