Probing the Cosmic Reionization History with JWST: Gunn-Peterson and Ly$α$ Damping Wing Absorption at $4.5 < z < 13$
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| Formato: | Preprint |
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2025
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| _version_ | 1866917172623704064 |
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| author | Umeda, Hiroya Ouchi, Masami Kageura, Yuta Harikane, Yuichi Nakane, Minami Thai, Tran Thi Nakajima, Kimihiko |
| author_facet | Umeda, Hiroya Ouchi, Masami Kageura, Yuta Harikane, Yuichi Nakane, Minami Thai, Tran Thi Nakajima, Kimihiko |
| contents | We present a statistical analysis of Ly$α$ absorption using 581 galaxies at $z=4.5$--13 observed with multiple JWST/NIRSpec spectroscopy programs, including JADES, UNCOVER, CEERS, and GO/DDT. We carefully construct composite spectra binned by redshift with homogeneous UV properties (UV magnitudes, UV slopes, and Ly$α$ equivalent widths) and identify significant Ly$α$ forest signals in galaxies at $z\sim5$--6, which diminish toward higher redshifts. We also find UV continuum breaks at rest-frame 1216 Å that soften beyond $z\gtrsim6$, confirming the effects of cosmic reionization through a self-consistent transition from Gunn-Peterson to Ly$α$ damping wing absorption in galaxies. Fair comparisons of composite spectra with matched UV magnitudes and slopes across redshift reveal that UV-faint galaxies clearly show stronger Ly$α$ absorption than UV-bright galaxies towards high redshift, providing insights into the topological evolution of reionization. We estimate Ly$α$ transmission at the Gunn-Peterson trough and Ly$α$ damping wing absorption by comparing the galaxy spectra to low-$z$ ($z\sim2$-5) galaxy templates that include galactic and circumgalactic absorption and Ly$α$ emission. Using these measurements together with reionization simulations, we derive volume average neutral hydrogen fractions of $\langle x_{\rm HI} \rangle$ = ${0.00}^{+0.12}_{-0.00}$, ${0.25}^{+0.10}_{-0.20}$, ${0.65}^{+0.27}_{-0.35}$, ${1.00}^{+0.00}_{-0.20}$, and ${1.00}^{+0.00}_{-0.40}$ at $z\sim5$, 6, 7, 9, and 10, respectively. These values broadly align with a reionization history characterized by a rapid transition around $z\sim7$--8, consistent with Ly$α$ emitter observations. While the physical driver of this rapid reionization remains unclear, it may involve the emergence of hidden AGN populations and/or the onset of Lyman-continuum escape from galaxies. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_04683 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Probing the Cosmic Reionization History with JWST: Gunn-Peterson and Ly$α$ Damping Wing Absorption at $4.5 < z < 13$ Umeda, Hiroya Ouchi, Masami Kageura, Yuta Harikane, Yuichi Nakane, Minami Thai, Tran Thi Nakajima, Kimihiko Astrophysics of Galaxies We present a statistical analysis of Ly$α$ absorption using 581 galaxies at $z=4.5$--13 observed with multiple JWST/NIRSpec spectroscopy programs, including JADES, UNCOVER, CEERS, and GO/DDT. We carefully construct composite spectra binned by redshift with homogeneous UV properties (UV magnitudes, UV slopes, and Ly$α$ equivalent widths) and identify significant Ly$α$ forest signals in galaxies at $z\sim5$--6, which diminish toward higher redshifts. We also find UV continuum breaks at rest-frame 1216 Å that soften beyond $z\gtrsim6$, confirming the effects of cosmic reionization through a self-consistent transition from Gunn-Peterson to Ly$α$ damping wing absorption in galaxies. Fair comparisons of composite spectra with matched UV magnitudes and slopes across redshift reveal that UV-faint galaxies clearly show stronger Ly$α$ absorption than UV-bright galaxies towards high redshift, providing insights into the topological evolution of reionization. We estimate Ly$α$ transmission at the Gunn-Peterson trough and Ly$α$ damping wing absorption by comparing the galaxy spectra to low-$z$ ($z\sim2$-5) galaxy templates that include galactic and circumgalactic absorption and Ly$α$ emission. Using these measurements together with reionization simulations, we derive volume average neutral hydrogen fractions of $\langle x_{\rm HI} \rangle$ = ${0.00}^{+0.12}_{-0.00}$, ${0.25}^{+0.10}_{-0.20}$, ${0.65}^{+0.27}_{-0.35}$, ${1.00}^{+0.00}_{-0.20}$, and ${1.00}^{+0.00}_{-0.40}$ at $z\sim5$, 6, 7, 9, and 10, respectively. These values broadly align with a reionization history characterized by a rapid transition around $z\sim7$--8, consistent with Ly$α$ emitter observations. While the physical driver of this rapid reionization remains unclear, it may involve the emergence of hidden AGN populations and/or the onset of Lyman-continuum escape from galaxies. |
| title | Probing the Cosmic Reionization History with JWST: Gunn-Peterson and Ly$α$ Damping Wing Absorption at $4.5 < z < 13$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2504.04683 |