AI 中文总结
该研究基于DIVER巡天的JWST观测数据，发现z~5.2星系过密区Lyα可见度较低，推导得到不同红移的中性分数上限，表明z~8时已存在斑块状再电离，Lyα可见度可编码电离拓扑与近源气体结构。
AI 中文摘要
莱曼α（Lyα）发射被广泛用于追踪宇宙再电离过程，但其解读取决于Lyα可见度随星系环境的变化规律。我们利用JWST/NIRSpec的深场观测数据，该数据来自“再电离纪元紫外光谱深度洞察（DIVER）”项目，覆盖 GOODS-N天区，测量了4.8<z<11范围内250个星系的Lyα可见度。样本包含84个Lyα探测结果，其中44个为强发射体，其静止帧Lyα等值宽度W_Lyα>25埃。我们将这些测量结果与JWST/NIRCam宽场无狭缝光谱巡天得到的氢α（Hα）和[O III]发射体数据结合，绘制了每个DIVER星系周围的密度场。具有高Lyα等值宽度（W_Lyα>25埃）或高有效Lyα逃逸分数（f_esc,Lyα^eff>0.05）的星系，相较于Lyα可见度较低的星系，往往距离附近的Hα和[O III]发射体更远。最清晰的信号出现在z~5.2的显著GOODS-N过密区附近，该区域中仅有不到15%的星系表现出强Lyα发射。这一趋势与最简单的“由内向外”再电离预期相反，后者认为过密区会产生更大的电离区域并提升Lyα可见度。可能的解释包括星系晕周介质与局域星系际介质的不透明度、致密吸收体以及气体运动学。我们还推导了f_esc,Lyα^eff的经验上限包络，并结合再电离模拟对其进行校准。将该包络解读为极限星系际介质衰减信号，可得到z~5.2、5.8、6.7、7.7、9.8处的中性分数上限分别为<x_HI>_max=0.36、0.76、0.74、0.84和1.0。z~8处的上限不支持该epoch存在几乎完全中性的星系际介质。这些结果表明，z~8时已存在斑块状再电离，且星系的Lyα可见度同时编码了大尺度电离拓扑结构与近源气体结构信息。
英文摘要
Ly-alpha emission is widely used to trace cosmic reionization, but its interpretation depends on how Ly-alpha visibility varies with galaxy environment. We use deep JWST/NIRSpec observations from Deep Insights into UV Spectroscopy at the Epoch of Reionization (DIVER) in GOODS-N to measure Ly-alpha visibility for 250 galaxies at 4.8<z<11. The sample contains 84 Ly-alpha detections, including 44 strong emitters with rest-frame Ly-alpha equivalent width W_Lyalpha>25 A. We combine these measurements with H-alpha and [O III] emitters from JWST/NIRCam wide-field slitless spectroscopy to map the density field around each DIVER galaxy. Galaxies with high Ly-alpha equivalent widths (W_Lyalpha>25 A) or high effective Ly-alpha escape fractions (f_esc,Lyalpha^eff>0.05) tend to lie farther from nearby H-alpha and [O III] emitters than galaxies with lower Ly-alpha visibility. The clearest signal occurs near the prominent GOODS-N overdensity at z~5.2, where fewer than 15% of galaxies show strong Ly-alpha emission. This trend is opposite to the simplest inside-out reionization expectation that overdensities produce larger ionized regions and enhance Ly-alpha visibility. Possible explanations include circumgalactic and local intergalactic opacity, dense absorbers, and gas kinematics. We also derive an empirical upper envelope for f_esc,Lyalpha^eff and calibrate it with reionization simulations. Interpreting this envelope as a limiting IGM-attenuation signal gives neutral-fraction ceilings of <x_HI>_max=0.36, 0.76, 0.74, 0.84, and 1.0 at z~5.2, 5.8, 6.7, 7.7, and 9.8, respectively. The z~8 ceiling disfavors an almost completely neutral IGM at this epoch. These results support patchy reionization already underway by z~8 and show that galaxy Ly-alpha visibility encodes both large-scale ionization topology and near-source gas structure.
Comments30 pages, 17 figures, 3 tables; submitted to ApJ
