Mon. Not. R. Astron. Soc., 474, 5694-5703 (2018/March-2)
Nitrogen oxide in protostellar envelopes and shocks: the ASAI survey.
CODELLA C., VITI S., LEFLOCH B., HOLDSHIP J., BACHILLER R., BIANCHI E., CECCARELLI C., FAVRE C., JIMENEZ-SERRA I., PODIO L. and TAFALLA M.
Abstract (from CDS):
The high sensitivity of the IRAM 30-m Astrochemical Surveys At IRAM (ASAI) unbiased spectral survey in the mm window allows us to detect NO emission towards both the Class I object SVS13-A and the protostellar outflow shock L1157-B1. We detect the hyperfine components of the 2Π1/2J = 3/2 - 1/2 (at 151 GHz) and the 2Π1/2J = 5/2 - 3/2 (at 250 GHz) spectral pattern. The two objects show different NO profiles: (i) SVS13-A emits through narrow (1.5 km s–1) lines at the systemic velocity, while (ii) L1157-B1 shows broad (∼5 km s–1) blueshifted emission. For SVS13-A, the analysis leads to Tex >= 4 K, N(NO) <= 3 x 1015 cm–2, and indicates the association of NO with the protostellar envelope. In L1157-B1, NO is tracing the extended outflow cavity: Tex ≃ 4-5 K, and N(NO) = 5.5 ± 1.5 x 1015 cm–2. Using C18O, 13C18O, C17O, and 13C17O ASAI observations, we derive an NO fractional abundance less than ∼10–7 for the SVS13-A envelope, in agreement with previous measurements towards extended photodissociation regions (PDRs) and prestellar objects. Conversely, a definite X(NO) enhancement is measured towards L1157-B1, ∼6 x 10–6, showing that the NO production increases in shocks. The public code UCLCHEMwas used to interpret the NO observations, confirming that the abundance observed in SVS13-A can be attained in an envelope with a gas density of 105 cm–3 and a kinetic temperature of 40 K. The NO abundance in L1157-B1 is reproduced with pre-shock densities of 105 cm–3 subjected to a ∼45 km s–1 shock.
© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: formation - ISM: abundances - ISM: jets and outflows - ISM: molecules
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