SILVERRUSH. VI. A simulation of Lyα emitters in the reionization epoch and a comparison with Subaru Hyper Suprime-Cam survey early data

The survey of Lyman α emitters (LAEs) with Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al.), is producing massive data of LAEs at z ^>_∼ 6. Here we present LAE simulations to compare the SILVERRUSH data. In 162³ comoving Mpc³ boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined 2³ models depending on the presence or absence of dispersion of halo Lyα emissivity, dispersion of the halo Lyα optical depth, τ_α, and halo mass dependence of τ_α. The unique free parameter in our model, a pivot value of τ_α, is calibrated so as to reproduce the z = 5.7 Lyα luminosity function (LF) of SILVERRUSH. We compare our model predictions with Lyα LFs at z = 6.6 and 7.3, LAE angular auto-correlation functions (ACFs) at z = 5.7 and 6.6, and LAE fractions in Lyman break galaxies at 5 < z < 7. The Lyα LFs and ACFs are reproduced by multiple models, but the LAE fraction turns out to be the most critical test. The dispersion of τ_α and the halo mass dependence of τ_α are essential to explain all observations reasonably. Therefore, a simple model of one-to-one correspondence between halo mass and Lyα luminosity with a constant Lyα escape fraction has been ruled out. Based on our best model, we present a formula to estimate the intergalactic neutral hydrogen fraction, xHI, from the observed Lyα luminosity density at z ^>_∼ 6. We finally obtain xHI = 0.5⁺⁰₋₀^._.¹₃ as a volume-average at z = 7.3.