Witnessing the onset of reionization through Lyman-α emission at redshift 13
Abstract
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 300 Myr old3–5. Smooth turnovers of their UV continua have been interpreted as damping-wing absorption of Lyman-α (Ly-α), the principal hydrogen transition6–9. 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 Å (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 330 Myr after the Big Bang.
Article Details
Authors (37)
Joris Witstok
Peter Jakobsen
Roberto Maiolino
Jakob M. Helton
Benjamin D. Johnson
Brant E. Robertson
Sandro Tacchella
Alex J. Cameron
Renske Smit
Andrew J. Bunker
Aayush Saxena
Fengwu Sun
Stacey Alberts
Santiago Arribas
William M. Baker
Rachana Bhatawdekar
Kristan Boyett
Phillip A. Cargile
Stefano Carniani
Stéphane Charlot
Jacopo Chevallard
Mirko Curti
Emma Curtis-Lake
Francesco D’Eugenio
Daniel J. Eisenstein
Kevin N. Hainline
Gareth C. Jones
Nimisha Kumari
Michael V. Maseda
Pablo G. Pérez-González
Pierluigi Rinaldi
Jan Scholtz
Hannah Übler
Christina C. Williams
Christopher N. A. Willmer
Chris Willott
Yongda Zhu