Methyl Isocyanate, CH3NCO, in the ISM

D. T. Halfen, V. V. Ilyushin, and L. M. Ziurys,
reported on the
Interstellar Detection of Methyl Isocyanate CH3NCO in Sgr B2(N): A Link from Molecular Clouds to Comets
Astrophys. J. 812, Art. No. L5 (2015).
Several clear, slightly, and heavily blended features were detected in emission in a molecular line survey of Sagittarius B2(N) in the 4 and 3 mm wavelength region using the 12 m ARO dish. The molecule occurs in both main hot cores with similar column densities at rotational temperatures of about 25 K. It is less abundant than HNCO by about factors of 35 and 53.

J. Cernicharo1, Z. Kisiel, B. Tercero, L. Kolesniková, I. R. Medvedev, A. López, S. Fortman, M. Winnewisser, F. C. de Lucia, J. L. Alonso, and J.-C. Guillemin,
reported on the
A Rigorous Detection of Interstellar CH3NCO: An important Missing Species in Astrochemical Networks
Astron. Astrophys. 587, Art. No. L4 (2016).
Using extensive Orion KL molecular line survey data obtained with the IRAM 30 m telescope as well as ALMA Cycle 0 science verification data, the authors identified a plethora of transitions and characterized the physcal conditions.
Using the meanwhile public IRAM 30 m data on Sagittarius B2 from
A. Belloche, H. S. P. Müller, K. M. Menten, P. Schilke, and C. Comito:
Complex Organic Molecules in the Interstellar Medium: IRAM 30 m Line Survey of Sagittarius B2(N) and (M)
Astron. Astrophys. 559, Art. No. A47 (2013);
the authors also corrected and added assignments from the first paper and reanalyzed the physical conditions in that source. They find methynol, HNCO, and methyl cyanide to be more abundant in Sgr B2(N) by factors of about 40, 40, and 50, different from the two positions in Orion KL: 400, 15, and 10 for position A, and 200, 15, and 25 for position B.

N. F. W. Ligterink, A. Coutens, V. Kofman, H. S. P. Müller, R. T. Garrod, H. Calcutt, S. F. Wampfler, J. K. Jørgensen, H. Linnartz, and E. F. van Dishoeck
reported on
The ALMA-PILS survey: detection of CH3NCO towards the low-mass protostar IRAS 16293–2422 and laboratory constraints on its formation
Mon. Not. R. Astron. Soc. 469, 2219 – 2229 (2017);
in addition,
R. Martín-Doménech, V. M. Rivilla, I. Jiménez-Serra, D. Quénard, L. Testi, and J. Martín-Pintado
reported on the
Detection of methyl isocyanate (CH3NCO) in a solar-type protostar
Mon. Not. R. Astron. Soc. 469, 2230 – 2234 (2017).


Contributor(s): H. S. P. Müller; 10, 2015; 03, 2016; 07, 2017