Volume 576, April 2015
|Number of page(s)||11|
|Section||Interstellar and circumstellar matter|
|Published online||23 March 2015|
Search for methylamine in high mass hot cores⋆
1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
2 Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
3 Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbackstr. 1, 85748 Garching, Germany
Received: 21 August 2014
Accepted: 18 December 2014
Aims. We aim to detect methylamine, CH3NH2, 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, CH3NH2 cannot be formed from atom addition to CO whereas other NH2-containing molecules such as formamide, NH2CHO, can.
Methods. Submillimeter spectra of several massive hot core regions were taken with the James Clerk Maxwell Telescope (JCMT). Abundances are determined with the rotational diagram method where possible.
Results. Methylamine is not detected, giving upper limit column densities between 1.9−6.4 × 1016 cm-2 for source sizes corresponding to the 100 K envelope radius. Combined with previously obtained JCMT data analysed in the same way, abundance ratios of CH3NH2, NH2CHO and CH3CN with respect to each other and to CH3OH are determined. These ratios are compared with Sagittarius B2 observations, where all species are detected, and to hot core models.
Conclusions. 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.
Key words: astrochemistry / line: identification / methods: observational / stars: formation / ISM: abundances / ISM: molecules
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2015
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