Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA's Parsec-scale Maps
Shi, Yong1,2; Wang, Junzhi3; Zhang, Zhi-Yu1,2; Zhang, Qizhou4; Gao, Yu5,6; Zhou, Luwenjia1,2; Gu, Qiusheng1,2; Qiu, Keping1,2; Xia, Xiao-Yang7; Hao, Cai-Na7; Chen, Yanmei1,2
Corresponding AuthorShi, Yong(
AbstractMetals are thought to have profound effects on the internal structures of the molecular clouds in which stars are born. The absence of metals is expected to prevent gas from efficient cooling and fragmentation in theory. However, this effect has not yet been observed in low-metallicity environments, such as in the early universe and local dwarf galaxies, because of the lack of high-spatial-resolution maps of gas. We carried out Atacama Large Millimeter/submillimeter Array observations of the carbon monoxide (CO) J = 2-1 emission line at 1.4 parsec resolutions of a molecular cloud in DDO 70 at 7% solar metallicity, the most metal-poor galaxy currently known with a CO detection. In total, five clumps have been identified and they are found to more or less follow Larson's law. Since the CO emission exists in regions with visual extinction A(V) around 1.0, we converted this A(V) to the gas-mass surface density using a gas-to-dust ratio of 4594 2848 for DDO 70. We found that the CO clumps in DDO 70 exhibit significantly larger (on average four times) sizes than those at the same gas-mass surface densities in the massive star formation regions of the Milky Way. The existence of such large clumps appears to be consistent with theoretical expectations that gas fragmentation in low-metallicity clouds is suppressed. While our observation is only for one cloud in the galaxy, if it is representative, the above result implies suppressed gas fragmentation during the cloud collapse and star formation in the early universe.
KeywordGiant molecular clouds Dwarf irregular galaxies Interstellar medium
Indexed BySCI
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000525493000001
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Document Type期刊论文
Corresponding AuthorShi, Yong
Affiliation1.Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China
2.Nanjing Univ, Key Lab Modern Astron & Astrophys, Minist Educ, Nanjing 210093, Peoples R China
3.Chinese Acad Sci, Shanghai Astron Observ, 80 Nandan Rd, Shanghai 200030, Peoples R China
4.Harvard & Smithsonian, Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
5.Xiamen Univ, Dept Astron, Xiamen 361005, Fujian, Peoples R China
6.Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Peoples R China
7.Tianjin Normal Univ, Tianjin Astrophys Ctr, Tianjin 300387, Peoples R China
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Shi, Yong,Wang, Junzhi,Zhang, Zhi-Yu,et al. Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA's Parsec-scale Maps[J]. ASTROPHYSICAL JOURNAL,2020,892(2):10.
APA Shi, Yong.,Wang, Junzhi.,Zhang, Zhi-Yu.,Zhang, Qizhou.,Gao, Yu.,...&Chen, Yanmei.(2020).Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA's Parsec-scale Maps.ASTROPHYSICAL JOURNAL,892(2),10.
MLA Shi, Yong,et al."Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA's Parsec-scale Maps".ASTROPHYSICAL JOURNAL 892.2(2020):10.
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