Discovery of the elusive radical NCO and confirmation of HNCO in space.

The isocyanate radical (NCO) is the simplest molecule containing the backbone of the peptide bond, C(=O)-N. This bond has a prebiotic interest since is the one linking two amino acids to form large chains of proteins. It is also present in some organic molecules observed in space such as HNCO, NHCHO and CHNCO. In this letter we report the first detection in space of NCO towards the dense core L483. We also report the identification of the ion HNCO, definitively confirming its presence in space, and observations of HNCO, HOCN, and HCNO in the same source. For NCO, we derive a column density of 2.2×10 cm, which means that it is only ~5 times less abundant than HNCO. We find that HNCO, HOCN and HCNO have abundances relative to HNCO of 1/400, 1/80, and 1/160, respectively. Both NCO and HNCO are involved in the production of HNCO and several of its isomers. We have updated our previous chemical models involving NCO and the production of the CHNO isomers. Taking into account the uncertainties in the model, the observed abundances are reproduced relatively well. Indeed, the detection of NCO and HNCO in L483 supports the chemical pathways to the formation of the detected CHNO isomers. Sensitive observations of NCO in sources where other molecules containing the C(=O)-N subunit have been detected could help in elucidating its role in prebiotic chemistry in space.