Census of Ly$α$ Emission from $\sim 600$ Galaxies at $z=5-14$: Evolution of the Ly$α$ Luminosity Function and a Late Sharp Cosmic Reionization
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| Format: | Preprint |
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2025
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| _version_ | 1866908287995215872 |
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| author | Kageura, Yuta Ouchi, Masami Nakane, Minami Umeda, Hiroya Harikane, Yuichi Yoshiura, Shintaro Nakajima, Kimihiko Yajima, Hidenobu Thai, Tran Thi |
| author_facet | Kageura, Yuta Ouchi, Masami Nakane, Minami Umeda, Hiroya Harikane, Yuichi Yoshiura, Shintaro Nakajima, Kimihiko Yajima, Hidenobu Thai, Tran Thi |
| contents | 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 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 towards higher redshifts. We derive Ly$α$ luminosity functions from $z\sim 5$ to $z\sim 10-14$ with the observed Ly$α$ EW distributions and galaxy UV luminosity functions, and find a $\sim3$ dex decrease in number density at $L_\mathrm{Lyα}=10^{42}-10^{43}$ erg s$^{-1}$ over the redshift range. Notably, this study presents the first constraints on the Ly$α$ luminosity function at $z\sim 8-14$. We obtain the neutral hydrogen fractions of $x_\mathrm{HI}=0.17_{-0.16}^{+0.23}$, $0.63_{-0.28}^{+0.18}$, $0.79_{-0.21}^{+0.13}$, and $0.88_{-0.13}^{+0.11}$ at $z\sim6$, $7$, $8-9$, and $10-14$, respectively, via comparisons of the reionization models developed by semi-numerical simulations with 21cmFAST explaining the observations of Ly$α$, UV continuum, and Planck electron optical depth. The high $x_\mathrm{HI}$ values over $z\sim 7-14$ suggest a late and sharp reionization, with the primary reionization process occurring at $z\sim 6-7$. Such a late and sharp reionization is not easily explained by either a clumpy inter-galactic medium or sources of reionization in a classical faint-galaxy or a bright-galaxy/AGN scenario, unless a very high escape fraction or AGN duty cycle is assumed at $z\sim 6-7$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2501_05834 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Census of Ly$α$ Emission from $\sim 600$ Galaxies at $z=5-14$: Evolution of the Ly$α$ Luminosity Function and a Late Sharp Cosmic Reionization Kageura, Yuta Ouchi, Masami Nakane, Minami Umeda, Hiroya Harikane, Yuichi Yoshiura, Shintaro Nakajima, Kimihiko Yajima, Hidenobu Thai, Tran Thi Astrophysics of Galaxies 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 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 towards higher redshifts. We derive Ly$α$ luminosity functions from $z\sim 5$ to $z\sim 10-14$ with the observed Ly$α$ EW distributions and galaxy UV luminosity functions, and find a $\sim3$ dex decrease in number density at $L_\mathrm{Lyα}=10^{42}-10^{43}$ erg s$^{-1}$ over the redshift range. Notably, this study presents the first constraints on the Ly$α$ luminosity function at $z\sim 8-14$. We obtain the neutral hydrogen fractions of $x_\mathrm{HI}=0.17_{-0.16}^{+0.23}$, $0.63_{-0.28}^{+0.18}$, $0.79_{-0.21}^{+0.13}$, and $0.88_{-0.13}^{+0.11}$ at $z\sim6$, $7$, $8-9$, and $10-14$, respectively, via comparisons of the reionization models developed by semi-numerical simulations with 21cmFAST explaining the observations of Ly$α$, UV continuum, and Planck electron optical depth. The high $x_\mathrm{HI}$ values over $z\sim 7-14$ suggest a late and sharp reionization, with the primary reionization process occurring at $z\sim 6-7$. Such a late and sharp reionization is not easily explained by either a clumpy inter-galactic medium or sources of reionization in a classical faint-galaxy or a bright-galaxy/AGN scenario, unless a very high escape fraction or AGN duty cycle is assumed at $z\sim 6-7$. |
| title | Census of Ly$α$ Emission from $\sim 600$ Galaxies at $z=5-14$: Evolution of the Ly$α$ Luminosity Function and a Late Sharp Cosmic Reionization |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2501.05834 |