Molecules with a peptide link in protostellar shocks: a comprehensive study of L1157
Interstellar molecules with a peptide link -NH-C(=O)-, like formamide (NH2 CHO), acetamide (NH2 COCH3) and isocyanic acid (HNCO) are particularly interesting for their potential role in pre-biotic chemistry.
We have studied their emission in the protostellar shock regions L1157-B1 and L1157-B2, with the IRAM 30m telescope, as part of the ASAI Large Program. Analysis of the line profiles shows that the emission arises from the outflow cavities associated with B1 and B2.
Molecular abundance of = (0.41.1) 10 8 and (3.38.8) 10 8 are derived for formamide and isocyanic acid, respectively, from a simple rotational diagram analysis. Conversely, NH2 COCH3 was not detected down to a relative abundance of a few <= 10 10 . B1 and B2 appear to be among the richest Galactic sources of HNCO and NH2 CHO molecules. A tight linear correlation between their abundances is observed, suggesting that the two species are chemically related. Comparison with astrochemical models favours molecule formation on ice grain mantles, with NH2 CHO generated from hydrogenation of HNCO. E. Mendoza, B Lefloch, A. Lopez-Sepulcre, C. Ceccarelli, C. Codella, H. M. Boechat-Roberty, R. Bachiller (Submitted on 21 Aug 2014)
Comments: 11 pages, 9 figures. Accepted for publication in MNRAS Main Journal. Accepted 2014 August 19, in original form 2014 July 8
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1408.4857 [astro-ph.SR]
(or arXiv:1408.4857v1 [astro-ph.SR] for this version)
Submission history
From: Edgar Mendoza [v1] Thu, 21 Aug 2014 02:48:56 GMT (210kb)
