Publication Date:
2016-09-03
Description:
As part of the Large Program Astrochemical Surveys At IRAM, we have used the IRAM 30 m telescope to lead a systematic search for the emission of rotational transitions of P-bearing species between 80 and 350 GHz towards L1157-B1, a shock position in the solar-type star-forming region L1157. We report the detection of several transitions of PN and, for the first time, of pre-biotic molecule PO. None of these species are detected towards the driving protostar of the outflow L1157-mm. Analysis of the line profiles shows that PN arises from the outflow cavity, where SiO, a strong shock tracer, is produced. Radiative transfer analysis yields an abundance of 2.5 x 10 –9 and 0.9 x 10 –9 for PO and PN, respectively. These results imply a strong depletion (100) of phosphorus in the quiescent cloud gas. Shock modelling shows that atomic N plays a major role in the chemistry of PO and PN. The relative abundance of PO and PN brings constraints both on the duration of the pre-shock phase, which has to be ~10 6 yr, and on the shock parameters. The maximum temperature in the shock has to be larger than 4000 K, which implies a shock velocity of 40 km s –1 .
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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