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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,Boyang1,2,3,4; Li,Di1,2,3; Staveley-Smith,Lister4,5; Qian,Lei1,3; Wong,Tony6; Goldsmith,Paul7
2019-12-20
Source PublicationThe Astrophysical Journal
ISSN0004-637X
Volume887Issue:2
AbstractAbstract 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.
KeywordInterstellar medium Large Magellanic Cloud Molecular clouds Interstellar atomic gas Interstellar absorption Abundance ratios Metallicity Dwarf galaxies Radio astronomy the Milky Way
DOI10.3847/1538-4357/ab54cd
Language英语
WOS IDIOP:0004-637X-887-2-ab54cd
PublisherThe American Astronomical Society
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Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/28689
Collection中国科学院国家天文台
Affiliation1.National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, People’s Republic of China; liuboyang@nao.cas.cn, dili@nao.cas.cn
2.University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of China
3.CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, People’s Republic of China
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.ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
6.University of Illinois, 227 Astronomy Building, MC-221, 1002 W. Green Street, Urbana, IL 61801, USA
7.Jet Propulsion Laboratory, M/S 180-703, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
First Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
Recommended Citation
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).
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