The Parkes HI survey of the Magellanic System
The Parkes HI survey of the Magellanic System
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Parkes HI 麦哲伦星系巡天
DOI：
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发表时间：
2004
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通讯作者：
U. Sydney
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作者：
C. Bruens;J. Kerp;L. Staveley;U. Mebold;M. Putman;R. Haynes;P. Kalberla;E. Muller;M. Institut;U. Bonn;Australia Telescope National Facility;Csiro;D. O. Astronomy;U. Michigan;U. Sydney
我们用帕克斯望远镜对整个麦哲伦系统进行了第一次全采样、空间完整的高速度分辨率(V=1.0$KM S-1)测量。这项调查覆盖了大约24%的南方天空，使用的是≈5‘ 格网，角分辨率为$=14\farcm1$。为这项调查开发了一个完全自动化的数据简化方案，以处理大量的$\ion{H}{i}$光谱($1.5\x 10^6$)。经过汉宁平滑和极化平均的各个光谱的均方根亮度温度噪声为σ=0.12K，最终数据立方体的均方根噪声为$Sigma_rmRMS}约为0.05$K，有效角分辨率为≈16‘。本文介绍了离子{H}{I}气体的测量参数、数据归算和总体分布。大麦哲伦星云(LMC)和小麦哲伦星云(SMC)与巨大的气体特征--麦哲伦桥、界面区、麦哲伦流和前臂有关--如果所有的离子{H}{i}$质量M($\ion{H}{i}$)=$4.87\x 10^8~M_\ODOT\Left[d/55~{\rMKPC}\Right]^2$，则所有的$\ion{H}{i}$气体都位于55kpc的相同距离。大约三分之二的{H}{I}$气体位于麦哲伦云(麦哲伦桥和界面区)附近，25%的$\ion{H}{I}$气体与麦哲伦流有关。前臂的质量比麦哲伦流小四倍，相当于气态特征总质量的6%。我们分析了麦哲伦星云及其附近的速度场，引入了LMC静止标准框架。麦哲伦桥中的离子{H}{I}相对于麦哲伦云显示出较低的速度，这表明它们几乎是平行运动的，而界面区的气体具有明显较高的相对速度，这表明这些气体正在离开麦哲伦桥，形成麦哲伦流的一个新部分。前臂连接到靠近LMC延伸臂的麦哲伦大桥。麦哲伦流和前臂中的云在柱密度分布和线廓线形状上都表现出显著的差异。麦哲伦流中的气体比前臂中的气体分布更均匀。如果前臂处于相当低的z高度，并且嵌入在较高压力的环境介质中，则可以解释这些形态差异。
We present the first fully and uniformly sampled, spatially complete $\ion{H}{i}$ survey of the entire Magellanic System with high velocity resolution ($\Delta v = 1.0$ km s -1 ), performed with the Parkes Telescope. Approximately 24 percent of the southern sky was covered by this survey on a ≈ 5´ grid with an angular resolution of ${\it HPBW} = 14\farcm1$. A fully automated data-reduction scheme was developed for this survey to handle the large number of $\ion{H}{i}$ spectra ($1.5\times10^6$). The individual Hanning smoothed and polarization averaged spectra have an rms brightness temperature noise of σ = 0.12 K. The final data-cubes have an rms noise of $\sigma_{\rm rms} \approx 0.05$ K and an effective angular resolution of ≈ 16´. In this paper we describe the survey parameters, the data-reduction and the general distribution of the $\ion{H}{i}$ gas. The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are associated with huge gaseous features – the Magellanic Bridge, the Interface Region, the Magellanic Stream, and the Leading Arm – with a total $\ion{H}{i}$ mass of M ($\ion{H}{i}$) = $4.87\times10^8~M_\odot \left[d/55~{\rm kpc}\right]^2$, if all $\ion{H}{i}$ gas is at the same distance of 55 kpc. Approximately two thirds of this $\ion{H}{i}$ gas is located close to the Magellanic Clouds (Magellanic Bridge and Interface Region), and 25% of the $\ion{H}{i}$ gas is associated with the Magellanic Stream. The Leading Arm has a four times lower $\ion{H}{i}$ mass than the Magellanic Stream, corresponding to 6% of the total $\ion{H}{i}$ mass of the gaseous features. We have analyzed the velocity field of the Magellanic Clouds and their neighborhood introducing a LMC-standard-of-rest frame. The $\ion{H}{i}$ in the Magellanic Bridge shows low velocities relative to the Magellanic Clouds suggesting an almost parallel motion, while the gas in the Interface Region has significantly higher relative velocities indicating that this gas is leaving the Magellanic Bridge building up a new section of the Magellanic Stream. The Leading Arm is connected to the Magellanic Bridge close to an extended arm of the LMC. The clouds in the Magellanic Stream and the Leading Arm show significant differences, both in the column density distribution and in the shapes of the line profiles. The $\ion{H}{i}$ gas in the Magellanic Stream is more smoothly distributed than the gas in the Leading Arm. These morphological differences can be explained if the Leading Arm is at considerably lower z -heights and embedded in a higher pressure ambient medium.