SILVERRUSH. XIV. Lya Luminosity Functions and Angular Correlation Functions from ~20,000 Lya Emitters at z~2.2-7.3 from upto 24 ${\mathrm{d}\mathrm{e}\mathrm{g}}^2$ HSC-SSP and CHORUS Surveys: Linking the Post-Reionization Epoch to the Heart of Reionization

We present the luminosity functions (LFs) and angular correlation functions (ACFs) derived from 18,960 Ly$\alpha$ emitters (LAEs) at $z=2.2-7.3$ over a wide survey area of $\lesssim 24\mathrm{d}\mathrm{e}{\mathrm{g}}^2$ that are identified in the narrowband data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) and the Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS) surveys. Confirming the large sample with the 241 spectroscopically identified LAEs, we determine Ly$\alpha$ LFs and ACFs in the brighter luminosity range down to $0.5L_{\star }$, and confirm that our measurements are consistent with previous studies but offer significantly reduced statistical uncertainties. The improved precision of our ACFs allows us to clearly detect one-halo terms at some redshifts, and provides large-scale bias measurements that indicate hosting halo masses of $\sim {10}^{11}{M}_{\odot }$ over $z\simeq 2-7$. By comparing our Ly$\alpha$ LF (ACF) measurements with reionization models, we estimate the neutral hydrogen fractions in the intergalactic medium to be $x_{\text{HI}}<0.05$ (=${0.06}_{-0.03}^{+0.12}$), $0.15_{-0.08}^{+0.10}$ (${0.21}_{-0.14}^{+0.19}$), $0.18_{-0.12}^{+0.14}$, and $0.75_{-0.13}^{+0.09}$ at $z=5.7$, $6.6$, $7.0$, and $7.3$, respectively. Our findings suggest that the neutral hydrogen fraction remains relatively low, $x_{\text{HI}}\lesssim 0.2$, at $z=5-7$, but increases sharply at $z>7$, reaching $x_{\text{HI}}\sim 0.9$ by $z\simeq 8-9$, as indicated by recent JWST studies. The combination of our results from LAE observations with recent JWST observations suggests that the major epoch of reionization occurred around $z\sim 7-8$, likely driven by the emergence of massive sources emitting significant ionizing photons.