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
Yuta Kageura, Masami Ouchi, Minami Nakane, Hiroya Umeda, Yuichi Harikane, Shintaro Yoshiura, Kimihiko Nakajima, Hidenobu Yajima, Tran Thi Thai
Abstract
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.