JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at $z=7-12$ Obtained with Ly$α$ Damping Wing Absorptions in 27 Bright Continuum Galaxies
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arXiv
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| Natura: | Preprint |
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2023
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| author | Umeda, Hiroya Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Xu, Yi Isobe, Yuki Zhang, Yechi |
| author_facet | Umeda, Hiroya Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Xu, Yi Isobe, Yuki Zhang, Yechi |
| contents | We present volume-averaged neutral hydrogen fractions $x_{\rm \HI}$ and ionized bubble radii $R_{\rm b}$ measured with Ly$α$ damping wing absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by CEERS, GO-1433, DDT-2750, and JADES programs, and obtain a sample containing 27 bright UV-continuum ($M_{\rm UV}<-18.5~{\rm mag}$) galaxies at $7<z<12$. We construct 4 composite spectra binned by redshift, and find the clear evolution of softening break towards high redshift at the rest-frame $1216$ Å, suggesting the increase of Ly$α$ damping wing absorption. We estimate Ly$α$ damping wing absorption in the galaxy spectra with realistic templates including Ly$α$ emission and circum-galactic medium absorptions. Assuming the standard inside-out reionization picture having an ionized bubble with radius $R_b$ around a galaxy embedded in the intergalactic medium with $x_{\rm \HI}$, we obtain $x_{\rm \HI}$ ($R_{\rm b}$) values generally increasing (decreasing) from $x_{\rm \HI}={0.53}^{+0.18}_{-0.47}$ to ${0.92}^{+0.08}_{-0.10}$ ($\log R_{\rm b}={1.67}^{+0.14}_{-0.16}$ to ${-0.69}^{+0.89}_{-0.24}$ comoving Mpc) at redshift $7.12^{+0.06}_{-0.08}$ to $9.91^{+1.49}_{-1.15}$. The redshift evolution of $x_{\rm \HI}$ indicates a moderately late reionization history consistent with the one previously suggested from the electron scattering of cosmic microwave background and the evolution of UV luminosity function with an escape fraction $f_{\rm esc}\sim 0.2$. Our ${R_{\rm b}}$ measurements suggest that bubble sizes could be up to a few dex larger than the cosmic average values estimated by analytic calculations for a given $x_{\rm \HI}$, while our $R_{\rm b}$ measurements are roughly comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2306_00487 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at $z=7-12$ Obtained with Ly$α$ Damping Wing Absorptions in 27 Bright Continuum Galaxies Umeda, Hiroya Ouchi, Masami Nakajima, Kimihiko Harikane, Yuichi Ono, Yoshiaki Xu, Yi Isobe, Yuki Zhang, Yechi Astrophysics of Galaxies We present volume-averaged neutral hydrogen fractions $x_{\rm \HI}$ and ionized bubble radii $R_{\rm b}$ measured with Ly$α$ damping wing absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by CEERS, GO-1433, DDT-2750, and JADES programs, and obtain a sample containing 27 bright UV-continuum ($M_{\rm UV}<-18.5~{\rm mag}$) galaxies at $7<z<12$. We construct 4 composite spectra binned by redshift, and find the clear evolution of softening break towards high redshift at the rest-frame $1216$ Å, suggesting the increase of Ly$α$ damping wing absorption. We estimate Ly$α$ damping wing absorption in the galaxy spectra with realistic templates including Ly$α$ emission and circum-galactic medium absorptions. Assuming the standard inside-out reionization picture having an ionized bubble with radius $R_b$ around a galaxy embedded in the intergalactic medium with $x_{\rm \HI}$, we obtain $x_{\rm \HI}$ ($R_{\rm b}$) values generally increasing (decreasing) from $x_{\rm \HI}={0.53}^{+0.18}_{-0.47}$ to ${0.92}^{+0.08}_{-0.10}$ ($\log R_{\rm b}={1.67}^{+0.14}_{-0.16}$ to ${-0.69}^{+0.89}_{-0.24}$ comoving Mpc) at redshift $7.12^{+0.06}_{-0.08}$ to $9.91^{+1.49}_{-1.15}$. The redshift evolution of $x_{\rm \HI}$ indicates a moderately late reionization history consistent with the one previously suggested from the electron scattering of cosmic microwave background and the evolution of UV luminosity function with an escape fraction $f_{\rm esc}\sim 0.2$. Our ${R_{\rm b}}$ measurements suggest that bubble sizes could be up to a few dex larger than the cosmic average values estimated by analytic calculations for a given $x_{\rm \HI}$, while our $R_{\rm b}$ measurements are roughly comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations. |
| title | JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at $z=7-12$ Obtained with Ly$α$ Damping Wing Absorptions in 27 Bright Continuum Galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2306.00487 |