A Multiline Study of a High-mass Young Stellar Object in the Small Magellanic Cloud with ALMA: The Detection of Methanol Gas at 0.2 Solar Metallicity

We report the results of subparsec-scale submillimeter observations toward an embedded high-mass young stellar object in the Small Magellanic Cloud (SMC) with ALMA. Complementary infrared data obtained with the AKARI satellite and the Gemini South telescope are also presented. The target infrared po...

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Bibliographic Details
Published in:The Astrophysical journal 2018-08, Vol.862 (2), p.102
Main Authors: Shimonishi, Takashi, Watanabe, Yoshimasa, Nishimura, Yuri, Aikawa, Yuri, Yamamoto, Satoshi, Onaka, Takashi, Sakai, Nami, Kawamura, Akiko
Format: Article
Language:English
Subjects:
Astrochemistry
Astrophysics
circumstellar matter
Coordination compounds
Cores
Emission lines
Galaxies
Gas temperature
Infrared sources (astronomy)
ISM: abundances
ISM: molecules
Magellanic Clouds
Metallicity
Milky Way
Molecular clouds
Organic chemistry
radio lines: ISM
Solar neighborhood
Sulfur dioxide
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Summary:We report the results of subparsec-scale submillimeter observations toward an embedded high-mass young stellar object in the Small Magellanic Cloud (SMC) with ALMA. Complementary infrared data obtained with the AKARI satellite and the Gemini South telescope are also presented. The target infrared point source is spatially resolved into two dense molecular cloud cores; one is associated with a high-mass young stellar object (YSO core), while another is not associated with an infrared source (East core). The two cores are dynamically associated but show different chemical characteristics. Emission lines of CS, C33S, H2CS, SO, SO2, CH3OH, H13CO+, H13CN, SiO, and dust continuum are detected from the observed region. Tentative detection of HDS is also reported. The first detection of CH3OH in the SMC has a strong impact on our understanding of the formation of complex organic molecules in metal-poor environments. The gas temperature is estimated to be ∼10 K based on the rotation analysis of CH3OH lines. The fractional abundance of CH3OH gas in the East core is estimated to be (0.5-1.5) × 10−8, which is comparable to or marginally higher than those of similar cold sources in our Galaxy despite a factor of five lower metallicity in the SMC. This work provides observational evidence that an organic molecule like CH3OH, which is largely formed on grain surfaces, can be produced even in a significantly lower metallicity environment compared to the solar neighborhood. A possible origin of cold CH3OH gas in the observed dense core is discussed.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aacd0c