Cold Atomic Gas in the Small Magellanic Cloud
Cold Atomic Gas in the Small Magellanic Cloud
复制标题
小麦哲伦星云中的冷原子气体
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
L. Staveley
中科院分区：
文献类型：
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作者：
J. Dickey;U. Mebold;S. Stanimirović;L. Staveley
在这个项目中，我们确定了小麦哲伦星云原子介质中的热相混合物。更大的目的是研究矮不规则星系中星际介质的性质与银河系相比的差异。观测结果使用澳大利亚紧凑阵列望远镜测量了穿过 SMC 的 21 厘米线的吸收光谱，与帕克斯望远镜和紧凑阵列望远镜数据组合的 21 厘米发射光谱进行比较。将两者结合起来，我们发现冷相气体的丰度小于总 H I 的 15%。因此，冷相气体非常稀有，相对于总 H I 的丰度只有太阳邻近区域的一半左右，低于 LMC、M31、M33 或银河系太阳邻近区域中发现的数字。这与矮不规则星系条件下的加热/冷却平衡计算定性一致。此外，我们发现冷相云的温度非常低，通常为 40 K 或更低。这远低于银河系的标称扩散云温度 (50-100 K)。这表明，在 SMC 的致密冷云中，H I 可能比在银河系中更丰富，在银河系中，具有相似密度和温度的云主要是分子。
In this project, we determine the mixture of thermal phases in the atomic medium of the Small Magellanic Cloud. The larger purpose is to study the difference in properties of the interstellar medium in a dwarf irregular galaxy compared with the Milky Way. The observations used the Australia Telescope Compact Array to measure absorption spectra of the 21 cm line through the SMC, for comparison with 21 cm emission spectra from a combination of data from the Parkes and Compact Array telescopes. Using the two together, we find the abundance of cool-phase gas to be less than 15% of the total H I. Thus, the cool-phase gas is very scarce, only about half as abundant relative to the total H I as in the solar neighborhood, a lower figure than that found in the LMC, M31, M33, or the solar neighborhood of the Milky Way. This is in qualitative agreement with the heating/cooling equilibrium calculations for conditions in a dwarf irregular galaxy. In addition, we find the temperature of the cool-phase clouds to be very low, typically 40 K or less. This is much less than the nominal diffuse cloud temperature in the Milky Way (50-100 K). This suggests that the H I may be more abundant in dense cold clouds in the SMC than in the Milky Way, where clouds of similar density and temperature are largely molecular.