BROAD N2H+ EMISSION TOWARD THE PROTOSTELLAR SHOCK L1157-B1

作者：Codella C^*; Viti S; Ceccarelli C; Lefloch B; Benedettini M; Busquet G; Caselli P; Fontani F; Gomez Ruiz A; Podio L; Vasta M

来源：Astrophysical Journal, 2013, 776(1): 52.

DOI：10.1088/0004-637X/776/1/52

• ISM: abundances
• ISM: jets and outflows
• ISM: molecules

We present the first detection of N2H+ toward a low-mass protostellar outflow, namely, the L1157-B1 shock, at similar to 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 (%26gt;= 10(5) cm(-3)) gas associated with the large (20 %26apos;%26apos;-25 %26apos;%26apos;) cavities opened by the protostellar wind. We find an N2H+ column density of a few 10(12) cm (2) corresponding to an abundance of (2-8) x 10 (9). The N2H+ abundance can be matched by a model of quiescent gas evolved for more than 10(4) yr, i.e., for more than the shock kinematical age (similar or equal to 2000 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 10(4) cm(-3), and then further compressed and accelerated by the shock.

• 出版日期2013-10-10