Molecular Cloud Structure in the Magellanic Clouds: Effect of Metallicity
Molecular Cloud Structure in the Magellanic Clouds: Effect of Metallicity
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麦哲伦云中的分子云结构：金属丰度的影响
DOI：
10.1086/305584
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发表时间：
1997
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影响因子：
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通讯作者：
R. Booth
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文献类型：
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作者：
S. Pak;D. Jaffe;E. V. van Dishoeck;L. Johansson;R. Booth
中性云在低金属含量环境中的化学结构进行检查，特别强调H到H2和C+到CO的转换。我们观测了大麦哲伦云中剑鱼座30和N159/N160以及小麦哲伦云中DEM S 16、DEM S 37和LI-SMC 36的近红外H2（1，0）S（1）、（2，1）S（1）和（5，3）O（3）线以及12 CO J = 1 → 0线。我们发现，H2的排放是UV激发的，（弱）CO排放总是存在（在我们调查的区域）对H2和[C II]排放已被检测到的位置。使用PDR程序和辐射传输程序，我们模拟了球形云和大平面云的线辐射发射。由于[C II]发射和H2发射出现在云的表面上，并且因为这些线是光学薄的，所以这些线不受中性云和含CO核心的相对尺寸变化的影响，而光学厚的CO发射可以受到强烈的影响。云的大小是通过测量CO排放强度与给定大小的平面云模式预测的CO排放强度的偏差来估计的。平均云柱密度，因此它的大小，随着金属丰度的降低而增加。我们的结果与McKee的光电离调节星星形成理论相一致。
The chemical structure of neutral clouds in low-metallicity environments is examined, with particular emphasis on the H to H2 and C+ to CO transitions. We observed near-IR H2 (1, 0) S(1), (2, 1) S(1), and (5, 3) O(3) lines and the 12CO J = 1 → 0 line from 30 Doradus and N159/N160 in the Large Magellanic Cloud and from DEM S 16, DEM S 37, and LI-SMC 36 in the Small Magellanic Cloud. We find that the H2 emission is UV-excited and that (weak) CO emission always exists (in our surveyed regions) toward positions where H2 and [C II] emission have been detected. Using a PDR code and a radiative transfer code, we simulate the emission of line radiation from spherical clouds and from large planar clouds. Because [C II] emission and H2 emission arise on the surface of the cloud and because the lines are optically thin, these lines are not affected by changes in the relative sizes of the neutral cloud and the CO-bearing core, while the optically thick CO emission can be strongly affected. The sizes of clouds are estimated by measuring the deviation of CO emission strength from that predicted by a planar cloud model of a given size. The average cloud column density, and therefore its size, increases as the metallicity decreases. Our result agrees with the photoionization-regulated star formation theory of McKee.
Y.Harada，T.Sakano，K.Ueda：“Lenkotrine B4 对增强超级氧化物产生的效果”广岛 J Med Sci。
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