We present 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 ( SXDS ) 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 } \times 10 ^ { -4 } Mpc ^ { -3 } and L _ { Ly \alpha } ^ { * } = 4.4 _ { -0.6 } ^ { +0.6 } \times 10 ^ { 42 } erg s ^ { -1 } with a fixed \alpha = -1.5 , and indicates a decrease from z = 5.7 at the \gtrsim 90 % confidence level .
However , this decrease is not large , only \simeq 30 % in Ly \alpha 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 } _ { 100 } 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 } M _ { \odot } , and duty cycle of LAE population is roughly \sim 1 % albeit with large uncertainties .
The average of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of 251 \pm 16 km s ^ { -1 } .
We find no large evolution of 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 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 \gtrsim 7 .