Neutral ISM, Lyα, and Lyman-continuum in the Nearby Starburst Haro 11
Neutral ISM, Lyα, and Lyman-continuum in the Nearby Starburst Haro 11
复制标题
附近星暴 Haro 11 中的中性 ISM、Lyα 和莱曼连续谱
DOI：
10.3847/1538-4357/aa5d0a
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
J. Puschnig
中科院分区：
文献类型：
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作者：
T. Rivera;G. Östlin;M. Hayes;J. Puschnig
形成恒星的星系被认为是莱曼连续体（LyC）辐射的主要来源，负责早期宇宙的再电离。然而，对逃逸电离辐射的直接观测很少，逃逸率也很低。在局部宇宙中，只有10个发射体被观察到，典型的逃逸分数为百分之几。调节这种逃逸的机制需要随着红移而强烈地演变，以便解释再电离的时代。气体含量和星星形成反馈是主要的怀疑对象，已知它们既调节中性气体的覆盖范围，又随宇宙时间演化。在本文中，我们重新分析哈勃太空望远镜（HST）-宇宙起源摄谱仪（COS）光谱的第一个检测到的本地LyC泄漏，哈洛11。我们研究了LyC泄漏和Lyα线形状之间的联系，以及反馈影响的中性星际介质（ISM）性质，如运动学和气体分布。我们讨论了两个极端的光学薄，密度有界的ISM和一个千疮百孔的，光学厚，电离有界的ISM，以及如何哈洛11适合理论预测。我们发现，ISM模型最有可能是一种嵌在高度电离介质中的中性气体介质，其覆盖率为1，电离介质中的剩余中性气体柱密度高到足以使光学厚度达到Lyα，但低到足以使LyC至少部分透明，并且在Si ii中无法检测到。这表明，星星形成反馈和星系尺度的相互作用事件在打开电离辐射通过中性介质的通道方面发挥了重要作用。
Star-forming galaxies are believed to be a major source of Lyman continuum (LyC) radiation responsible for reionizing the early universe. Direct observations of escaping ionizing radiation have however been sparse and with low escape fractions. In the local universe, only 10 emitters have been observed, with typical escape fractions of a few percent. The mechanisms regulating this escape need to be strongly evolving with redshift in order to account for the epoch of reionization. Gas content and star formation feedback are among the main suspects, known to both regulate neutral gas coverage and evolve with cosmic time. In this paper, we reanalyze Hubble Space Telescope (HST)-Cosmic Origins Spectrograph (COS) spectrocopy of the first detected local LyC leaker, Haro 11. We examine the connection between LyC leakage and Lyα line shape, and feedback-influenced neutral interstellar medium (ISM) properties like kinematics and gas distribution. We discuss the two extremes of an optically thin, density bounded ISM and a riddled, optically thick, ionization bounded ISM, and how Haro 11 fits into theoretical predictions. We find that the most likely ISM model is a clumpy neutral medium embedded in a highly ionized medium with a combined covering fraction of unity and a residual neutral gas column density in the ionized medium high enough to be optically thick to Lyα, but low enough to be at least partly transparent to LyC and undetected in Si ii. This suggests that star formation feedback and galaxy-scale interaction events play a major role in opening passageways for ionizing radiation through the neutral medium.