2025ApJS..278...33K

We present the statistical properties of Lyα emission in 586 galaxies at z = 4.5-14.2, observed by multiple JWST/NIRSpec spectroscopy projects, including the JADES, GLASS, CEERS, and GO/DDT programs. We obtain Lyα equivalent width (EW), Lyα escape fraction, and ionizing photon production efficiency measurements or upper limits for these galaxies, and confirm that the Lyα-emitting galaxy fraction decreases toward higher redshifts. We derive Lyα luminosity functions from z ∼ 5 to z ∼ 10-14 with the observed Lyα EW distributions and galaxy UV luminosity functions, and find an ∼3 dex decrease in number density at L_Lyα = 10⁴²-10⁴³ erg s^–1 over the redshift range. Notably, this study presents the first constraints on the Lyα luminosity function at z ∼ 8-14. We obtain the neutral hydrogen fractions of ${x}_{{\rm{H}}\,{\rm\small{I}}}=0.1{7}_{-0.16}^{+0.23}$, $0.6{3}_{-0.28}^{+0.18}$, $0.7{9}_{-0.21}^{+0.13}$, and $0.8{8}_{-0.13}^{+0.11}$ at z ∼ 6, 7, 8-9, and 10-14, respectively, via comparisons of the reionization models developed by seminumerical simulations with 21cmFAST explaining the observations of Lyα, UV continuum, and Planck electron optical depth. The high x_H I_ values over z ∼ 7-14 suggest a late and sharp reionization, with the primary reionization process occurring at z ∼ 6-7. Such a late and sharp reionization is not easily explained by either a clumpy intergalactic medium or sources of reionization in a classical faint-galaxy or a bright-galaxy/active galactic nucleus (AGN) scenario, unless a very high escape fraction or AGN duty cycle is assumed at z ∼ 6-7.