Ly$α$ Emission at $z=7-13$: Clear Ly$α$ Equivalent Width Evolution Indicating the Late Cosmic Reionization History
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arXiv
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| Autori principali: | , , , , , , , , |
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| Natura: | Preprint |
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2023
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| _version_ | 1866910389530263552 |
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| author | Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Umeda, Hiroya Isobe, Yuki Zhang, Yechi Xu, Yi |
| author_facet | Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Umeda, Hiroya Isobe, Yuki Zhang, Yechi Xu, Yi |
| contents | We present the evolution of Ly$α$ emission derived from 53 galaxies at $z=6.6-13.2$ that are identified by multiple JWST/NIRSpec spectroscopy programs of ERS, GO, DDT, and GTO. These galaxies fall on the star-formation main sequence and are the typical star-forming galaxies with UV magnitudes of $-22.5\leq M_\mathrm{UV}\leq-17.0$. We find that 15 out of 53 galaxies show Ly$α$ emission at the $>3σ$ levels, and obtain Ly$α$ equivalent width (EW) measurements and stringent $3σ$ upper limits for the 15 and 38 galaxies, respectively. Confirming that Ly$α$ velocity offsets and line widths of our galaxies are comparable with those of low-redshift Ly$α$ emitters, we investigate the redshift evolution of the Ly$α$ EW. We find that Ly$α$ EWs statistically decrease towards high redshifts on the Ly$α$ EW vs. $M_{\rm UV}$ plane for various probability distributions of the uncertainties. We then evaluate neutral hydrogen fractions $x_{\rm HI}$ with the Ly$α$ EW redshift evolution and the cosmic reionization simulation results on the basis of a Bayesian inference framework, and obtain $x_{\rm HI}<0.79$, $=0.62^{+0.15}_{-0.36}$, and $0.93^{+0.04}_{-0.07}$ at $z\sim7$, $8$, and $9-13$, respectively. These moderately large $x_{\rm HI}$ values are consistent with the Planck CMB optical depth measurement and previous $x_{\rm HI}$ constraints from galaxy and QSO Ly$α$ damping wing absorptions, and strongly indicate a late reionization history. Such a late reionization history suggests that major sources of reionization would emerge late and be hosted by moderately massive halos in contrast with the widely-accepted picture of abundant low-mass objects for the sources of reionization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2312_06804 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Ly$α$ Emission at $z=7-13$: Clear Ly$α$ Equivalent Width Evolution Indicating the Late Cosmic Reionization History Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Umeda, Hiroya Isobe, Yuki Zhang, Yechi Xu, Yi Astrophysics of Galaxies We present the evolution of Ly$α$ emission derived from 53 galaxies at $z=6.6-13.2$ that are identified by multiple JWST/NIRSpec spectroscopy programs of ERS, GO, DDT, and GTO. These galaxies fall on the star-formation main sequence and are the typical star-forming galaxies with UV magnitudes of $-22.5\leq M_\mathrm{UV}\leq-17.0$. We find that 15 out of 53 galaxies show Ly$α$ emission at the $>3σ$ levels, and obtain Ly$α$ equivalent width (EW) measurements and stringent $3σ$ upper limits for the 15 and 38 galaxies, respectively. Confirming that Ly$α$ velocity offsets and line widths of our galaxies are comparable with those of low-redshift Ly$α$ emitters, we investigate the redshift evolution of the Ly$α$ EW. We find that Ly$α$ EWs statistically decrease towards high redshifts on the Ly$α$ EW vs. $M_{\rm UV}$ plane for various probability distributions of the uncertainties. We then evaluate neutral hydrogen fractions $x_{\rm HI}$ with the Ly$α$ EW redshift evolution and the cosmic reionization simulation results on the basis of a Bayesian inference framework, and obtain $x_{\rm HI}<0.79$, $=0.62^{+0.15}_{-0.36}$, and $0.93^{+0.04}_{-0.07}$ at $z\sim7$, $8$, and $9-13$, respectively. These moderately large $x_{\rm HI}$ values are consistent with the Planck CMB optical depth measurement and previous $x_{\rm HI}$ constraints from galaxy and QSO Ly$α$ damping wing absorptions, and strongly indicate a late reionization history. Such a late reionization history suggests that major sources of reionization would emerge late and be hosted by moderately massive halos in contrast with the widely-accepted picture of abundant low-mass objects for the sources of reionization. |
| title | Ly$α$ Emission at $z=7-13$: Clear Ly$α$ Equivalent Width Evolution Indicating the Late Cosmic Reionization History |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2312.06804 |