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

Cosmology and conventions

A flat ΛCDM cosmology is used throughout based on the latest results of the Planck Collaboration⁵², with H₀ = 67.4 km s⁻¹ Mpc⁻¹, Ω_m = 0.315 and Ω_b = 0.0492. The cosmic hydrogen fraction is fixed…