Statistics of 207 Lya Emitters at a Redshift Near 7: Constraints on
  Reionization and Galaxy Formation Models
  We present Lya luminosity function (LF), clustering measurements, and Lya
line profiles based on the largest sample, to date, of 207 Lya emitters (LAEs)
at z=6.6 on the 1-deg^2 sky of Subaru/XMM-Newton Deep Survey (SXDS) field. Our
z=6.6 Lya LF including cosmic variance estimates yields the best-fit Schechter
parameters of phi*=8.5 +3.0/-2.2 x10^(-4) Mpc^(-3) and L*(Lya)=4.4 +/-0.6
x10^42 erg s^(-1) with a fixed alpha=-1.5, and indicates a decrease from z=5.7
at the >~90% confidence level. However, this decrease is not large, only =~30%
in Lya luminosity, which is too small to be 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^(-1) Mpc and 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 Mo, and duty
cycle of LAE population is roughly ~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 Lya line profile from z=5.7
to 6.6, and no anti-correlation between Lya 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 IGM's Lya 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>~7.
