Search for methylamine in high mass hot cores

Abstract

We aim to detect methylamine, CH${}_3$NH${}_2$, in a variety of hot cores and use it as a test for the importance of photon-induced chemistry in ice mantles and mobility of radicals. Specifically, CH${}_3$NH${}_2$ cannot be formed from atom addition to CO whereas other NH${}_2$-containing molecules such as formamide, NH${}_2$CHO, can. Submillimeter spectra of several massive hot core regions were taken with the James Clerk Maxwell Telescope. Abundances are determined with the rotational diagram method where possible. Methylamine is not detected, giving upper limit column densities between 1.9 $-$ 6.4 $\times$ 10${}^{16}$ cm${}^{-2}$ for source sizes corresponding to the 100 K envelope radius. Combined with previously obtained JCMT data analyzed in the same way, abundance ratios of CH${}_3$NH${}_2$, NH${}_2$CHO and CH${}_3$CN with respect to each other and to CH${}_3$OH are determined. These ratios are compared with Sagittarius B2 observations, where all species are detected, and to hot core models. The observed ratios suggest that both methylamine and formamide are overproduced by up to an order of magnitude in hot core models. Acetonitrile is however underproduced. The proposed chemical schemes leading to these molecules are discussed and reactions that need further laboratory studies are identified. The upper limits obtained in this paper can be used to guide future observations, especially with ALMA.

arXiv comment14 pages, 5 figures, accepted for publication in A&A

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• Methylamine and other simple N-bearing species in the hot cores NGC 6334I MM1-3
• Detection of New Methylamine (CH${}_3$NH${}_2$) Sources: Candidates for Future Glycine Surveys
• CoCCoA: Complex Chemistry in hot Cores with ALMA. Selected oxygen-bearing species
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• Detection of possible glycine precursor molecule methylamine towards the hot molecular core G358.93$-$0.03 MM1