Systematic identification of LAEs for visible exploration and reionization research using Subaru HSC (SILVERRUSH). I. program strategy and clustering properties of ∼ 2, 000 Lyα emitters at z = 6 − 7 over the 0.3 − 0.5 Gpc² survey area

We present the SILVERRUSH program strategy and clustering properties investigated with ∼ 2, 000 Lyα emitters at z = 5.7 and 6.6 found in the early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrowband filters. We derive angular correlation functions with the unprecedentedly large samples of LAEs at z = 6 − 7 over the large total area of 14 − 21 deg² corresponding to 0.3 − 0.5 comoving Gpc². We obtain the average large-scale bias values of b_avg = 4.1 ± 0.2 (4.5 ± 0.6) at z = 5.7 (z = 6.6) for ≿ L^∗ LAEs, indicating the weak evolution of LAE clustering from z = 5.7 to 6.6. We compare the LAE clustering results with two independent theoretical models that suggest an increase of an LAE clustering signal by the patchy ionized bubbles at the epoch of reionization (EoR), and estimate the neutral hydrogen fraction to be xHI = 0.15⁺⁰₋₀^._.¹⁵₁₅ at z = 6.6. Based on the halo occupation distribution models, we find that the ≿ L^∗ LAEs are hosted by the dark-matter halos with the average mass of log(hM_h〉/M⊙) = 11.1⁺⁰₋₀^._.²₄ (10.8⁺⁰₋₀^._.³₅) at z = 5.7 (6.6) with a Lyα duty cycle of 1 % or less, where the results of z = 6.6 LAEs may be slightly biased, due to the increase of the clustering signal at the EoR. Our clustering analysis reveals the low-mass nature of ≿ L^∗ LAEs at z = 6 − 7, and that these LAEs probably evolve into massive super-L^∗ galaxies in the present-day universe.