Census of Ly<i>α</i> Emission from ∼600 Galaxies at <i>z</i> = 5–14: Evolution of the Ly<i>α</i> Luminosity Function and a Late Sharp Cosmic Reionization

Abstract We present the statistical properties of Ly α 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 Ly α equivalent width (EW), Ly α escape fraction, and ionizing photon production efficiency measurements or upper limits for these galaxies, and confirm that the Ly α -emitting galaxy fraction decreases toward higher redshifts. We derive Ly α luminosity functions from z ∼ 5 to z ∼ 10–14 with the observed Ly α EW distributions and galaxy UV luminosity functions, and find an ∼3 dex decrease in number density at L Ly α = 10 42 –10 43 erg s −1 over the redshift range. Notably, this study presents the first constraints on the Ly α luminosity function at z ∼ 8–14. We obtain the neutral hydrogen fractions of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mspace width="0.25em"/> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.23</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.28</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.18</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.7</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.21</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.8</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.11</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> 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 Ly α , 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.