We present volume-averaged neutral hydrogen fractions $x_{ \rm \HI}$ and ionized bubble radii $R_{ \rm b}$ measured with Ly$\alpha$ 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 $1216$ { \AA}, suggesting the increase of Ly$\alpha$ damping wing absorption. We estimate Ly$\alpha$ damping wing absorption in the galaxy spectra with realistic templates including Ly$\alpha$ 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.
Categories: astro-ph.GA