STATISTICS OF 207 Lyα EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS

We present the Ly alpha luminosity function (LF), clustering measurements, and Ly alpha line profiles based on the largest sample to date of 207 Ly alpha emitters (LAEs) at z = 6.6 on the 1 deg(2) sky of Subaru/XMM-Newton Deep Survey field. Our z = 6.6 Ly alpha LF including cosmic variance estimates yields the best-fit Schechter parameters of phi* = 8.5(-2.2)(+3.0) x 10(-4) Mpc(-3) and L*(Ly alpha) = 4.4(-0.6)(+0.6) x 10(42) erg s(-1) with a fixed alpha = -1.5, and indicates a decrease from z = 5.7 at the greater than or similar to 90% confidence level. However, this decrease is not large, only similar or equal to 30% in Ly alpha luminosity, which is too small to have been identified in the previous studies. A clustering signal of z = 6.6 LAEs is detected for the first time. We obtain the correlation length of r(0) = 2-5 h(100)(-1) Mpc and a bias of b = 3-6, and find no significant boost of clustering amplitude by reionization at z = 6.6. The average hosting dark halo mass inferred from clustering is 10(10)-10(11) M-circle dot, and a duty cycle of LAE population is roughly similar to 1%, albeit with large uncertainties. The average of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of 251 +/- 16 km s(-1). We find no large evolution of the Ly alpha line profile from z = 5.7 to 6.6, and no anti-correlation between Ly alpha luminosity and line width at z = 6.6. The combination of various reionization models and our observational results about the LF, clustering, and line profile indicates that there would exist a small decrease of the intergalactic medium's (IGM's) Ly alpha transmission owing to reionization, but that the hydrogen IGM is not highly neutral at z = 6.6. Our neutral-hydrogen fraction constraint implies that the major reionization process took place at z greater than or similar to 7.