外流或星系风：矮星系晕中电离气体的命运
Outflow or galactic wind: The fate of ionized gas in the halos of dwarf galaxies
摘要：
内容：恒星爆发的不规则星系的Hα图像揭示了大量扩展的电离气体结构，在某些情况下，距离当前恒星形成活动的任何地方都有kpc的距离。运动学分析，特别是昏暗的结构中的光环的矮星系允许洞察到的属性和这种气体成分的起源。这对于星系的化学演化、星系际介质的富集以及理解早期宇宙中星系的形成都是重要的。目的：我们想研究在两个不规则矮星系（NGC 2366和NGC 4861）中检测到的电离气体是否会被引力束缚在宿主星系上，或者可以通过成为自由流动的风而逃离宿主星系。研究方法：获得了NGC 2366和NGC 4861的非常深的Hα图像，以探测和编目小尺度和大尺度电离气体结构，直到非常低的表面亮度。随后，对Hα线进行了高分辨率长缝阶梯光栅光谱学，以详细分析最突出的细丝和壳。为了计算两个星系的逃逸速度，并将其与探测到的细丝和壳层的膨胀速度进行比较，我们使用了暗物质晕模型。结果如下：我们在Hα图像上探测到了大量的小尺度（最多几百pc）和大尺度（直径或长度约1-2 kpc）电离气体结构。许多较暗的是新发现的。中阶梯光谱揭示了外流和膨胀的气泡/壳层，速度在20和110 km/s之间。其中一些结构与Hα图像中的细丝一致。与NFW暗物质晕模型导出的星系的逃逸速度的比较表明，所有的气体特征保持引力约束。
英文摘要：
Context: Hαimages of star bursting irregular galaxies reveal a large amount of extended ionized gas structures, in some cases at kpc-distance away from any place of current star forming activity. A kinematic analysis of especially the faint structures in the halo of dwarf galaxies allows insights into the properties and the origin of this gas component. This is important for the chemical evolution of galaxies, the enrichment of the intergalactic medium, and for the understanding of the formation of galaxies in the early universe. Aims: We want to investigate whether the ionized gas detected in two irregular dwarf galaxies (NGC 2366 and NGC 4861) stays gravitationally bound to the host galaxy or can escape from it by becoming a freely flowing wind. Methods: Very deep Hαimages of NGC 2366 and NGC 4861 were obtained to detect and catalog both small and large scale ionized gas structures down to very low surface brightnesses. Subsequently, high-resolution long-slit echelle spectroscopy of the Hαline was performed for a detailed kinematic analysis of the most prominent filaments and shells. To calculate the escape velocity of both galaxies and to compare it with the derived expansion velocities of the detected filaments and shells, we used dark matter halo models. Results: We detected a huge amount of both small scale (up to a few hundred pc) and large scale (about 1-2 kpc of diameter or length) ionized gas structures on our Hαimages. Many of the fainter ones are new detections. The echelle spectra reveal outflows and expanding bubbles/shells with velocities between 20 and 110 km/s. Several of these structures are in accordance with filaments in the Hαimages. A comparison with the escape velocities of the galaxies derived from the NFW dark matter halo model shows that all gas features stay gravitationally bound.
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