论文标题

h $α$距离麦哲伦流的领先臂的距离

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

论文作者

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

论文摘要

领先的手臂是潮汐功能,它通过银河系的光环在其轨道上的麦芽云云前。领先臂的许多物理特性,例如其质量和大小,由于距离测量很少而受到限制。虽然H $α$测量已被用来估计光环云的距离,但许多研究在检测领先组的H $α$方面没有成功。在这项研究中,我们探索了一组H i云,这些云是$ 75^{\ circ} -90^{\ circ} $从麦哲伦云中。通过紫外线和21厘米的无线电光谱法,该区域被称为领先的臂延伸,与领先的臂具有化学和运动学相似性。使用威斯康星州H $α$映射器,我们在七个目标中的四分之四发现了H $α$的排放。假设该区域主要是光电离的,我们使用一个辐射模型,该模型结合了Galaxy,Magellanic Clouds和$ \ rm z = 0 $的贡献,以得出$ d _ {\ odot} \ ge13.4〜kpc $的地狱性中心距离。我们还使用此模型来重新添加$ d _ {\ odot} \ geq 5.0 $ kpc和$ d _ {\ odot} \ geq 22.9〜kpc $ to the文献中可能与领先的臂相关的两个云。使用这些新的测量值以及文献中的其他测量值,我们提供了领先的臂式距离距离麦哲伦河流经度的变化的一般趋势,并探索了其对领先ARM的原点和最接近的方法的影响。

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.

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