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Title:Testing Dust-surface Formation Model Of Prebiotic Molecule Ch3nco In Star-forming Core Sagittarius B2(n1) By Alma
Author(s):Araki, Mitsunori
Contributor(s):Tsukiyama, Koichi; Kuze, Nobuhiko; Takano, Shuro; Oyama, Takahiro; Ohno, Yuki; Izuoka, Kyoichi
Abstract:Origin of organic molecules on Earth is discussed to be interstellar clouds, because comets carried molecules produced in clouds. Methyl isocyanate CH$_{3}$NCO is presumably one of the delivered organic molecules at the primitive earth. However, observed abundance ratios of [CH$_{3}$NCO]/[HNCO] in molecular clouds [1] are clearly lower than that in the comet 67P [2]. Recently a theoretical study has suggested that this abundance anomaly can be explained by a model of dust-surface formation of CH$_{3}$NCO in molecular clouds [3]. If that is the case, high-temperature CH$_{3}$NCO desorbed from dust surface makes a compact distribution in a central region of a star-forming core. To examine this temperature and distribution condition, the spatial and spectral data of CH$_{3}$NCO toward the (N1) core of the star-forming region Sagittarius B2 observed by ALMA were investigated in the 94–113 GHz region for 24 rotational lines. Considering intensity maps and velocity structures, a compact distribution relating to a bipolar molecular flow and an accretion disk already suggested [4] was imaged by CH$_{3}$NCO. Rotational temperatures are 20–60 K and column densities are 10$^{15}$ cm$^{-2}$. These results suggest hot and dense conditions of this molecule in the central region of the core. Hence, CH$_{3}$NCO detected in the present data is likely to be produced on dust surface. The model explaining the abundance anomaly is observationally supported. [1] Halfen et al., 2015, ApJL, 812, L5. [2] Goesmann et al., 2015, Sci., 349, 6247. [3] Majumdar et al., 2018, MNRAS, 473, L59. [4] Lis et al. 1993, ApJ, 402, 238.
Issue Date:2021-06-25
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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