JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at $z=7-12$ Obtained with Ly$\alpha$ Damping Wing Absorptions in 27 Bright Continuum Galaxies

We present volume-averaged neutral hydrogen fractions $x_{\text{HI}}$ and ionized bubble radii $R_{\mathrm{b}}$ 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 ($M_{\mathrm{U}\mathrm{V}}<-18.5\mathrm{m}\mathrm{a}\mathrm{g}$) 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$\alpha$ 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 $x_{\text{HI}}$, we obtain $x_{\text{HI}}$ ($R_{\mathrm{b}}$) values generally increasing (decreasing) from $x_{\text{HI}}={0.53}_{-0.47}^{+0.18}$ to ${0.92}_{-0.10}^{+0.08}$ ($\log R_{\mathrm{b}}={1.67}_{-0.16}^{+0.14}$ to ${-0.69}_{-0.24}^{+0.89}$ comoving Mpc) at redshift $7.12_{-0.08}^{+0.06}$ to $9.91_{-1.15}^{+1.49}$. The redshift evolution of $x_{\text{HI}}$ 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 $f_{\mathrm{e}\mathrm{s}\mathrm{c}}\sim 0.2$. Our $R_{\mathrm{b}}$ 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 $x_{\text{HI}}$, while our $R_{\mathrm{b}}$ measurements are roughly comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations.