An ATCA Survey of H i Absorption in the Magellanic Clouds. I. H i Gas Temperature Measurements in the Small Magellanic Cloud
An ATCA Survey of H i Absorption in the Magellanic Clouds. I. H i Gas Temperature Measurements in the Small Magellanic Cloud
复制标题
ATCA 对麦哲伦星云中 Hi 吸收的调查。
DOI：
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发表时间：
2019
影响因子：
8.7
通讯作者：
T. Wong
中科院分区：
文献类型：
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作者：
K. Jameson;N. McClure;Boyang Liu;J. Dickey;L. Staveley;S. Stanimirović;J. Dempsey;Joanne Dawson;H. Dénes;A. Bolatto;Di Li;T. Wong
我们展示了一项新的澳大利亚望远镜紧凑型阵列H - i对两个麦哲伦云的吸收调查的小麦哲伦云部分的第一批结果，包括超过800小时的观测。我们的新氢吸收线数据使我们能够测量低金属丰度环境中冷中性气体的温度和分数。我们观察了22个独立的场，总共针对55个连续源，其中37个我们检测到H吸收；由此我们测得柱密度加权平均自旋温度= 150k。将光谱分解为单独的吸收谱线特征，我们估计了不同气体组分的温度，并发现该样品的平均冷气体温度为~ 30k，低于银河系的平均温度~ 40k。H似乎均匀地分布在整个SMC中，我们在我们的样品中检测到67%的视线吸收，包括星系主体外的一些吸收（NH i cm−2）。冷中性原子气体的光学深度和温度在位置、空间和速度上没有明显的变化趋势。尽管存在低金属丰度环境，但我们发现平均冷气体比例为~ 20%，与银河系没有什么不同。
We present the first results from the Small Magellanic Cloud portion of a new Australia Telescope Compact Array H i absorption survey of both of the Magellanic Clouds, comprising over 800 hr of observations. Our new H i absorption line data allow us to measure the temperature and fraction of cold neutral gas in a low-metallicity environment. We observed 22 separate fields, targeting a total of 55 continuum sources, against 37 of which we detected H i absorption; from this we measure a column-density-weighted mean average spin temperature of = 150 K. Splitting the spectra into individual absorption line features, we estimate the temperatures of different gas components and find an average cold gas temperature of ∼30 K for this sample, lower than the average of ∼40 K in the Milky Way. The H i appears to be evenly distributed throughout the SMC, and we detect absorption in 67% of the lines of sight in our sample, including some outside the main body of the galaxy (NH i cm−2). The optical depth and temperature of the cold neutral atomic gas show no strong trend with location spatially or in velocity. Despite the low-metallicity environment, we find an average cold gas fraction of ∼20%, not dissimilar from that of the Milky Way.