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arXiv · 2604.13267

The Great Escape of ionizing photons during Cosmic Morning

Kanak Saha·Roland Bacon·Anne Verhamme·Soumil Maulick·Akio Inoue·Souradeep Bhattacharya·Marc Rafelski·Edmund Christian Herenz·Rogier Windhorst·Michael Rutkowski·Shyam N. Tandon
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Abstract

The end of the Cosmic Dark Age marked the onset of reionization, driven by extreme-UV photons from the first galaxies. Direct detection of such photons has remained challenging due to strong intergalactic attenuation. Here, we report the first direct detection of ionizing photons at rest-frame wavelengths $350\r{A}$, $392\r{A}$, and $485\r{A}$, using deep UV imaging from two independent space observatories: AstroSat and HST. These photons emerge from a stacked sample of spectroscopically confirmed Ly$\alpha$ emitters at $5.9 24.6\ $eV provide evidence that HeI reionization has begun by this epoch.

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Kanak Saha, Roland Bacon, Anne Verhamme, Soumil Maulick, Akio Inoue, Souradeep Bhattacharya, Marc Rafelski, Edmund Christian Herenz, Rogier Windhorst, Michael Rutkowski, Shyam N. Tandon. 2026-04-14. The Great Escape of ionizing photons during Cosmic Morning. https://arxiv.org/abs/2604.13267

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