Escape of Lyα Emission in the Starburst Galaxy Markarian 357: a Wind’s Far Side
Escape of Lyα Emission in the Starburst Galaxy Markarian 357: a Wind’s Far Side
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星暴星系 Markarian 357 中 Lyα 发射的逃逸：风的远方
DOI：
10.1086/428371
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
W. Keel
中科院分区：
文献类型：
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作者：
W. Keel
在星暴星系Mrk 357中，利用哈勃太空望远镜成像和无缝光谱学研究了强Lyα辐射从星际介质中逃逸的位置。Hα图像显示，电离气体主要是在全球风中，而不是与光学和紫外连续体中看到的单个恒星形成区域有关。Lyα辐射主要来自风结构的西北侧，相对于光线有明显的红移。这两种性质都是看到光子线从长形或双极星暴风的远端反向散射的特征，符合逃逸计算和高红移星系中净发射Lyα的风的证据。散射最重要的是在这种风本身，而不是涉及周围的中性介质，正如在探测到的发射的中心和边缘之间线峰的相对红移从250到≈30 km s-1所示。与恒星光和Hα结构相比，Lyα发射具有很强的不对称性。这些结果进一步证明，运动学，而不是气体金属丰度或尘埃含量，是决定哪个星系有强烈的Lyα辐射的主要因素，并且在莱曼断裂星系和Lyα线辐射中发现的那些星系中，强大的（也许是偶然的）恒星爆发是常见的。
Hubble Space Telescope imaging and slitless spectroscopy are used to examine where the strong Lyα emission escapes from the interstellar medium in the starburst galaxy Mrk 357. An Hα image shows that the ionized gas is mostly in a global wind, rather than associated with the individual star-forming regions seen in the optical and UV continuum. The Lyα emission comes predominantly from the northwest side of the wind structure spatially, and shows a significant redshift relative to the optical lines. Both of these properties are signatures of seeing the line photons backscattered from the far side of a prolate or bipolar starburst wind, fitting both with escape calculations and evidence for winds in high-redshift galaxies with net Lyα emission. Scattering is most important within this wind itself, rather than involving a surrounding neutral medium, as shown by the decreasing relative redshift of the line peak from 250 to ≈30 km s-1 between the center and edge of the detected emission. The Lyα emission exhibits strong asymmetry in comparison with both the starlight and Hα structures. These results add to the evidence that kinematics, rather than gas metallicity or dust content, are the dominant effect in determining which galaxies have strong Lyα emission, and that powerful (and perhaps episodic) starbursts are common among Lyman break galaxies as well as those discovered from Lyα line emission.