Tracing the Formation of Molecular Clouds in a Low-metallicity Galaxy: An H i Narrow Self-absorption Survey of the Large Magellanic Cloud

doi:10.3847/1538-4357/ab54cd

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	Tracing the Formation of Molecular Clouds in a Low-metallicity Galaxy: An H i Narrow Self-absorption Survey of the Large Magellanic Cloud
	Liu,Boyang 4,5,6,7; Li,Di 5,6,7; Staveley-Smith,Lister 3,4; Qian,Lei 5,7; Wong,Tony 2; Goldsmith,Paul 1
刊名	The Astrophysical Journal
	2019-12-20
卷号	887 期号:2
关键词	Interstellar medium Large Magellanic Cloud Molecular clouds Interstellar atomic gas Interstellar absorption Abundance ratios Metallicity Dwarf galaxies Radio astronomy the Milky Way
ISSN号	0004-637X
DOI	10.3847/1538-4357/ab54cd
英文摘要	Abstract Cold atomic hydrogen clouds are the precursors of molecular clouds. Due to self-absorption, the opacity of cold atomic hydrogen may be high, and this gas may constitute an important mass component of the interstellar medium. Atomic hydrogen gas can be cooled to temperatures much lower than found in the cold neutral medium through collisions with molecular hydrogen. In this paper, we search for H i narrow self-absorption (HINSA) features in the Large Magellanic Cloud (LMC) as an indicator of such cold H i clouds, and use the results to quantify atomic masses and atomic-to-molecular gas ratio. Our search for HINSA features was conducted toward molecular clouds in the LMC using the ATCA+Parkes H i survey and the MAGMA CO survey. HINSA features are prevalent in the surveyed sightlines. This is the first detection of HINSA in an external galaxy. The HINSA-H i/ ratio in the LMC varies from 0.5?×?10?3 to 3.4?×?10?3 (68% interval), with a mean value of (1.31?±?0.03)?×?10?3, after correcting for the effect of foreground H i gas. This is similar to the Milky Way value and indicates that similar fractions of cold gas exist in the LMC and the Milky Way, despite their differing metallicities, dust content and radiation fields. The low ratio also confirms that, as with the Milky Way, the formation timescale of molecular clouds is short. The ratio shows no radial gradient, unlike the case for stellar metallicity. No correlation is found between our results and those from previous H i absorption studies of the LMC.
语种	英语
出版者	The American Astronomical Society
WOS记录号	IOP:0004-637X-887-2-AB54CD
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/28688]
专题	中国科学院国家天文台
作者单位	1.Jet Propulsion Laboratory, M/S 180-703, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 2.University of Illinois, 227 Astronomy Building, MC-221, 1002 W. Green Street, Urbana, IL 61801, USA 3.ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 4.International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia lister.staveley-smith@uwa.edu.au 5.CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, People’s Republic of China 6.University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of China 7.National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, People’s Republic of China; liuboyang@nao.cas.cn, dili@nao.cas.cn
推荐引用方式 GB/T 7714	Liu,Boyang,Li,Di,Staveley-Smith,Lister,et al. Tracing the Formation of Molecular Clouds in a Low-metallicity Galaxy: An H i Narrow Self-absorption Survey of the Large Magellanic Cloud[J]. The Astrophysical Journal,2019,887(2).
APA	Liu,Boyang,Li,Di,Staveley-Smith,Lister,Qian,Lei,Wong,Tony,&Goldsmith,Paul.(2019).Tracing the Formation of Molecular Clouds in a Low-metallicity Galaxy: An H i Narrow Self-absorption Survey of the Large Magellanic Cloud.The Astrophysical Journal,887(2).
MLA	Liu,Boyang,et al."Tracing the Formation of Molecular Clouds in a Low-metallicity Galaxy: An H i Narrow Self-absorption Survey of the Large Magellanic Cloud".The Astrophysical Journal 887.2(2019).