Infalling gas in a Lyman-α blob
Infalling gas in a Lyman-α blob
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DOI：
10.1038/s41550-020-1033-3
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发表时间：
2020-03
期刊：
影响因子：
14.1
通讯作者：
Y. Ao;Zheng Zheng-Zheng;C. Henkel;S. Nie;A. Beelen;R. Cen;M. Dijkstra;P. Francis;J. Geach;K. Kohno;M. Lehnert;K. Menten;Junzhi Wang;A. Weiss
中科院分区：
文献类型：
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作者：
Y. Ao;Zheng Zheng-Zheng;C. Henkel;S. Nie;A. Beelen;R. Cen;M. Dijkstra;P. Francis;J. Geach;K. Kohno;M. Lehnert;K. Menten;Junzhi Wang;A. Weiss
Lyman-α斑点(实验室)是在Lyman-α(Lyα)氢谱线上空间延伸的发射星云，红移很大，最常见于恒星形成星系的致密环境中。最近的一项研究表明，高红移星系周围的Lyα辐射覆盖了几乎100%的天空。实验室中Lyα排放的来源仍不清楚，也存在争议。正如最近的模拟所证明的那样，它可能是由涉及星系超风/流出的光致电离、来自恒星爆发或活动星系核的Lyα光子的共振散射、或来自星系上吸积的冷气流的冷却辐射来提供动力的。在这里，我们分析了实验室内的气体运动学，为气体流入提供了罕见的观测证据。这与冷流辐射Lyα光子时引力吸积能的释放是一致的。这也为中央星系可能存在的冷流提供了直接证据。与恒星形成消耗的气体质量相比，流入气体的质量并不重要，也不是Lyα发射的主要动力源，但它暗示了另一种机制来解释年轻星系周围扩展的Lyα发射的起源。
Lyman-α blobs (LABs) are spatially extended nebulae of emission in the Lyman-α (Lyα) line of hydrogen, seen at high redshifts,, and most commonly found in the dense environment of star-forming galaxies,. A recent study showed that nearly 100% of the sky is covered by Lyα emission around high-redshift galaxies, –. The origin of Lyα emission in the LABs is still unclear and under debate. It may be powered by photoionization involving galactic superwinds/outflows, resonant scattering of Lyα photons from starbursts or active galactic nuclei, , , , , , –, or by cooling radiation from cold streams of gas accreting onto galaxies,, as demonstrated by recent simulations. Here we analyse the gas kinematics within a LAB, providing rare observational evidence for infalling gas. This is consistent with the release of gravitational accretion energy as cold streams radiate Lyα photons. It also provides direct evidence for possible cold streams feeding the central galaxies. The mass of the infalling gas is not important in comparison to the gas mass consumed by star formation, and is also not the major powering source of Lyα emission, but it hints at another mechanism to explain the origin of the extended Lyα emission around young galaxies.