arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.09606astro-ph.GA
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H $α$到麦哲伦流前缘臂的距离

H$α$ Distances to the Leading Arm of the Magellanic Stream

Jacqueline Antwi-Danso, Kathleen A. Barger, L. Matthew Haffner

备注：
13 pages, 5 figures, published in ApJ
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摘要：

引导臂是一个潮汐特征，位于麦哲伦云的前面，在它们穿过银河系晕的轨道上。引导臂的许多物理属性，例如其质量和尺寸，由于其具有很少的距离测量，因此约束很差。虽然H $α$测量已被用来估计晕云的距离，许多研究一直未能成功地检测H $α$从领先的手臂。在这项研究中，我们探讨了一组H I云的谎言$75^{\circ} - 90^{\circ}$从麦哲伦云。通过紫外线和21厘米的无线电光谱，这一地区，被称为领先的手臂延伸，被发现有化学和运动学的相似性的领先Arm.Using威斯康星H $α$映射器，我们检测到H $α$发射在我们的七个目标中的四个。假设这一地区主要是光电离，我们使用的辐射模型，结合银河系的贡献，麦哲伦云，并在$\rm z = 0$河外背景推导出一个日心距离$d_{\odot}\ge13.4~kpc$。我们还使用这个模型来重新推导H $α$距离的$d_{\odot} \geq 5.0$ kpc和$d_{\odot} \geq 22.9~kpc$的两个云在文献中，也可能与领先的手臂。使用这些新的测量，和其他文献中，我们提供了一个总的趋势的变化领先的手臂日心距离作为麦哲伦流经度的函数，并探索其对引导臂的起源和最接近点的影响。

英文摘要：

The Leading Arm is a tidal feature that is in front of the Magellanic Clouds on their orbit through the Galaxy's halo. Many physical properties of the Leading Arm, such as its mass and size, are poorly constrained because it has few distance measurements. While H$α$ measurements have been used to estimate the distances to halo clouds, many studies have been unsuccessful in detecting H$α$ from the Leading Arm. In this study, we explore a group of H I clouds which lie $75^{\circ} - 90^{\circ}$ from the Magellanic Clouds. Through ultraviolet and 21-cm radio spectroscopy, this region, dubbed the Leading Arm Extension, was found to have chemical and kinematic similarities to the Leading Arm. Using the Wisconsin H$α$ Mapper, we detect H$α$ emission in four out of seven of our targets. Assuming that this region is predominantly photoionized, we use a radiation model that incorporates the contributions of the Galaxy, Magellanic Clouds, and the extragalactic background at $\rm z = 0$ to derive a heliocentric distance of $d_{\odot}\ge13.4~kpc$. We also use this model to rederive H$α$ distances of $d_{\odot} \geq 5.0$ kpc and $d_{\odot} \geq 22.9~kpc$ to two clouds in the literature that might also be associated with the Leading Arm. Using these new measurements, and others in the literature, we provide a general trend of the variation of Leading Arm heliocentric distance as a function of Magellanic Stream longitude, and explore its implications for the origin and closest point of approach of the Leading Arm.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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