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题名: ABUNDANCES AND ISOTOPE RATIOS IN THE MAGELLANIC CLOUDS: THE STAR-FORMING ENVIRONMENT OF N 113
作者: Wang Min(王旻)1, 2; Chin, Y. -N.3; Henkel, C.2; Whiteoak, J. B.4; Cunningham, M.5
刊名: ASTROPHYSICAL JOURNAL
出版日期: 2009
卷号: 690, 期号:1, 页码:580-597
关键词: galaxies: abundances ; galaxies: individual (LMC) ; Magellanic Clouds ; radio continuum: galaxies ; radio lines: galaxies
DOI: 10.1088/0004-637X/690/1/580
文章类型: Article
英文摘要: With the goal of deriving the physical and chemical conditions of star-forming regions in the Large Magellanic Cloud (LMC), a spectral line survey of the prominent star-forming region N 113 is presented. The observations cover parts of the frequency range from 85 GHz to 357 GHz and include 63 molecular transitions from a total of 16 species, among them are the spectra of rare isotopologues. Maps of selected molecular lines as well as the 1.2 mm continuum distribution are also presented. Molecular abundances in the core of the complex are consistent with a photon-dominated region in a nitrogen deficient environment. While carbon monoxide (CO) shows optical depths of the order of tau similar to 10, (13)CO is optically thin. The most prominent lines of carbon monosulfide (CS), HCN, and HCO(+) show signs of weak saturation (tau similar to 0.5). Densities range from 5 x 10(3) cm(-3) for CO to almost 10(6) for CS, HCN, and a few other species, indicating that only the densest regions provide sufficient shielding, even for some of the most common species. An ortho- to para-formaldehyde (H(2)CO) ratio of similar to 3 hints at H(2)CO formation in a warm (greater than or similar to 40 K) environment. Isotope ratios are (12)C/(13)C similar to 49 +/- 5, (16)O/(18)O similar to 2000 +/- 250, (18)O/(17)O similar to 1.7 +/- 0.2, and (32)S/(34)S similar to 15. Agreement with data from other star-forming clouds shows that the gas is well mixed in the LMC. The isotope ratios not only differ from those seen in the Galaxy, they also do not form a continuation of the trends observed with decreasing metallicity from the inner to the outer Galaxy. This implies that the outer Galaxy, even though showing an intermediate metallicity, is not providing a transition zone between the inner Galaxy and the metal-poor environment of the Magellanic Clouds. A part of this discrepancy is likely caused by differences in the age of the stellar populations in the outer Galaxy and the LMC. While, however, this scenario readily explains measured carbon and oxygen isotope ratios, nitrogen and sulfur still lack a self-consistent interpretation.
WOS标题词: Science & Technology ; Physical Sciences
类目[WOS]: Astronomy & Astrophysics
研究领域[WOS]: Astronomy & Astrophysics
关键词[WOS]: DENSE INTERSTELLAR CLOUDS ; GRAIN SURFACE-CHEMISTRY ; SEST KEY PROGRAM ; MOLECULAR CLOUDS ; NEARBY GALAXIES ; COLLISIONAL EXCITATION ; H2O MASERS ; (CO)-O-18/(CO)-O-17 RATIO ; CHEMICAL EVOLUTION ; FORMALDEHYDE ORTHO
收录类别: SCI
语种: 英语
WOS记录号: WOS:000262726600048
Citation statistics:
内容类型: 期刊论文
URI标识: http://libir.pmo.ac.cn/handle/332002/15934
Appears in Collections:星系中的恒星形成研究团组_期刊论文

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作者单位: 1.Acad Sinica, Purple Mt Observ, Nanjing 210008, Peoples R China
2.Max Planck Inst Radioastron, D-53121 Bonn, Germany
3.Tamkang Univ, Dept Phys, Tamsui 25137, Taipei County, Taiwan
4.CSIRO, Radiophys Labs, Australia Telescope Natl Facil, Epping, NSW 2121, Australia
5.Univ New S Wales, Sch Phys, Sydney, NSW 2052, Australia
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