Spectral Shapes of the Lyα Emission from Galaxies. I. Blueshifted Emission and Intrinsic Invariance with Redshift
Spectral Shapes of the Lyα Emission from Galaxies. I. Blueshifted Emission and Intrinsic Invariance with Redshift
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星系 Lyα 发射的光谱形状 I. 蓝移发射和红移的本征不变性。
DOI：
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发表时间：
2020
影响因子：
4.9
通讯作者：
C. Scarlata
中科院分区：
文献类型：
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作者：
M. Hayes;A. Runnholm;M. Gronke;C. Scarlata
我们证明了恒星形成星系的H i Lyα发射光谱轮廓的红移演化。在第一项研究中，我们特别注意蓝移发射的贡献。在红移z = 2.9-6.6时，我们用甚大望远镜的多单元光谱探测器识别了229个Lyα选择星系的样本，而在低z（< 0.44）时，我们使用哈勃太空望远镜上的宇宙起源光谱仪观测到的74个紫外选择星系的样本。在星系际介质（IGM）的吸收可以忽略的低z区，Lyα线中心向蓝和向红的光度之比（LB/R）随等效宽度（WLyα）的增加而迅速增加。然而，这种相关性不会出现在z = 3-4时，我们使用自举模拟来证明LB/R的趋势应该被IGM吸收的变化所抑制。我们的主要结果是，观测到的蓝移贡献随着红移的增加而迅速下降：在z = 0时LB/R = 30%，但在z = 3时下降到15%，到z = 6时下降到3%以下。进一步模拟IGM吸收对未吸收COS光谱的影响，我们证明蓝翼贡献的减少完全归因于Lyα吸收系统的增厚，而不需要来自局域结构、伴星系或宇宙陨坑的额外H i不透明度。我们根据数值辐射传输模拟、星系总Lyα和电离输出的演化以及再电离时期分辨Lyα谱的实用性讨论了我们的结果。
We demonstrate the redshift evolution of the spectral profile of H i Lyα emission from star-forming galaxies. In this first study we pay special attention to the contribution of blueshifted emission. At redshift z = 2.9–6.6, we compile spectra of a sample of 229 Lyα-selected galaxies identified with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope, while at low z ( < 0.44) we use a sample of 74 ultraviolet-selected galaxies observed with the Cosmic Origin Spectrograph on board the Hubble Space Telescope. At low z, where absorption from the intergalactic medium (IGM) is negligible, we show that the ratio of Lyα luminosity blueward and redward of line center (LB/R) increases rapidly with increasing equivalent width (WLyα). This correlation does not, however, emerge at z = 3–4, and we use bootstrap simulations to demonstrate that trends in LB/R should be suppressed by variations in IGM absorption. Our main result is that the observed blueshifted contribution evolves rapidly downward with increasing redshift: LB/R ≈ 30% at z ≈ 0, but dropping to 15% at z ≈ 3, and to below 3% by z ≈ 6. Applying further simulations of the IGM absorption to the unabsorbed COS spectrum, we demonstrate that this decrease in the blue-wing contribution can be entirely attributed to the thickening of intervening Lyα absorbing systems, with no need for additional H i opacity from local structure, companion galaxies, or cosmic infall. We discuss our results in light of the numerical radiative transfer simulations, the evolving total Lyα and ionizing output of galaxies, and the utility of resolved Lyα spectra in the reionization epoch.