近日，英国剑桥大学Zhu, Yongda团队发现通过红移13处的莱曼-α发射见证再电离的开始。相关论文于2025年3月26日发表在《自然》杂志上。

宇宙再电离始于首批星系产生的紫外线（UV）辐射照亮充斥着原始宇宙的冷中性气体之时。詹姆斯•韦伯太空望远镜（JWST）的最新观测表明，在宇宙年龄不足 3 亿年时，就有出人意料的紫外明亮星系存在于红移z = 14之外的区域。这些星系紫外线连续谱的平滑翻转被解释为主要氢跃迁的莱曼-α（Ly-α）阻尼翼吸收。然而，这些来源的关键特性（如其浮现辐射场）在很大程度上仍难以捉摸。

研究组报告了来自 JWST 深空星系外观测（JADES）对一个红移 z = 13.0 星系的光谱学观测结果，其呈现出一条独特的明亮发射线，明确被识别为 Ly-α，以及一个平滑翻转。他们观测到EWLy-α的等效宽度> 40 A（静止帧），此前仅在星系间介质逐渐电离的 z < 9 区域观测到。结合极蓝的紫外线连续谱，意外的 Ly-α 发射表明该星系是大量产生和泄漏电离光子的源头。

这表明，大质量、炽热的恒星或活跃星系核创建了一个早期再电离区域，从而阻止了Ly-α线的完全消失，这为最早期星系的性质以及大爆炸后仅 3.3 亿年就出现的再电离现象提供了新的见解。

附：英文原文

Title: Witnessing the onset of reionization through Lyman-α emission at redshift 13

Author: Witstok, Joris, Jakobsen, Peter, Maiolino, Roberto, Helton, Jakob M., Johnson, Benjamin D., Robertson, Brant E., Tacchella, Sandro, Cameron, Alex J., Smit, Renske, Bunker, Andrew J., Saxena, Aayush, Sun, Fengwu, Alberts, Stacey, Arribas, Santiago, Baker, William M., Bhatawdekar, Rachana, Boyett, Kristan, Cargile, Phillip A., Carniani, Stefano, Charlot, Stphane, Chevallard, Jacopo, Curti, Mirko, Curtis-Lake, Emma, DEugenio, Francesco, Eisenstein, Daniel J., Hainline, Kevin N., Jones, Gareth C., Kumari, Nimisha, Maseda, Michael V., Prez-Gonzlez, Pablo G., Rinaldi, Pierluigi, Scholtz, Jan, bler, Hannah, Williams, Christina C., Willmer, Christopher N. A., Willott, Chris, Zhu, Yongda

Issue&Volume: 2025-03-26

Abstract: Cosmic reionization began when ultraviolet (UV) radiation produced in the first galaxies began illuminating the cold, neutral gas that filled the primordial Universe1,2. Recent James Webb Space Telescope (JWST) observations have shown that surprisingly UV-bright galaxies were in place beyond redshift z=14, when the Universe was less than 300Myr old3,4,5. Smooth turnovers of their UV continua have been interpreted as damping-wing absorption of Lyman-α (Ly-α), the principal hydrogen transition6,7,8,9. However, spectral signatures encoding crucial properties of these sources, such as their emergent radiation field, largely remain elusive. Here we report spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES10) of a galaxy at redshift z=13.0 that reveals a singular, bright emission line unambiguously identified as Ly-α, as well as a smooth turnover. We observe an equivalent width of EWLy-α>40 (rest frame), previously only seen at z<9 where the intervening intergalactic medium becomes increasingly ionized11. Together with an extremely blue UV continuum, the unexpected Ly-α emission indicates that the galaxy is a prolific producer and leaker of ionizing photons. This suggests that massive, hot stars or an active galactic nucleus have created an early reionized region to prevent complete extinction of Ly-α, thus shedding new light on the nature of the earliest galaxies and the onset of reionization only 330Myr after the Big Bang.

DOI: 10.1038/s41586-025-08779-5

Source: https://www.nature.com/articles/s41586-025-08779-5