During the epoch of reionization, the first galaxies were enshrouded in pristine neutral gas, with one of the brightest emission lines in star-forming galaxies, Lyman α (Lyα), expected to remain undetected until the Universe became ionized. Providing an explanation for the surprising detection of Lyα in these early galaxies is a major challenge for extragalactic studies. Recent James Webb Space Telescope observations have reignited the debate about whether residence in an overdense galaxy is a sufficient and necessary condition for Lyα to escape. Here, we take unique advantage of both high-resolution and high-sensitivity images from the James Webb Space Telescope Near Infrared Camera to show that all galaxies in a sample of Lyα emitters with redshift >7 have close companions. We exploit on-the-fly radiative-transfer magnetohydrodynamical simulations with cosmic ray feedback to show that galaxies with frequent mergers have very bursty star formation histories that drives episodes of high intrinsic Lyα emission and facilitates the escape of Lyα photons along channels cleared of neutral gas. We conclude that the rapid buildup of stellar mass through mergers presents a compelling solution to the long-standing puzzle of the detection of Lyα emission deep in the epoch of reionization.

在再电离时期，第一个星系被原始的中性气体所笼罩，其中恒星形成星系中最亮的发射线之一莱曼α（Lyα）预计在宇宙电离之前不会被发现。为这些早期星系中令人惊讶的 Lyα 发现提供解释是河外研究的主要挑战。最近詹姆斯·韦伯太空望远镜的观测重新引发了关于居住在密度过大的星系中是否是 Lyα 逃逸的充分必要条件的争论。在这里，我们利用詹姆斯·韦伯太空望远镜近红外相机的高分辨率和高灵敏度图像的独特优势来表明，红移 >7 的 Lyα 发射体样本中的所有星系都有紧密的伴星。我们利用宇宙射线反馈的动态辐射转移磁流体动力学模拟来表明，频繁合并的星系具有非常爆发的恒星形成历史，这会驱动高内在 Lyα 发射的事件，并促进 Lyα 光子沿着清除了中性气体的通道逃逸。我们的结论是，通过合并恒星质量的快速积累为再电离时代深处检测 Lyα 发射这一长期存在的难题提供了一个令人信服的解决方案。