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

Abstract

We present Lya luminosity function (LF), clustering measurements, and Lya\nline profiles based on the largest sample, to date, of 207 Lya emitters (LAEs)\nat z=6.6 on the 1-deg^2 sky of Subaru/XMM-Newton Deep Survey (SXDS) field. Our\nz=6.6 Lya LF including cosmic variance estimates yields the best-fit Schechter\nparameters of phi*=8.5 +3.0/-2.2 x10^(-4) Mpc^(-3) and L*(Lya)=4.4 +/-0.6\nx10^42 erg s^(-1) with a fixed alpha=-1.5, and indicates a decrease from z=5.7\nat the >~90% confidence level. However, this decrease is not large, only =~30%\nin Lya luminosity, which is too small to be identified in the previous studies.\nA clustering signal of z=6.6 LAEs is detected for the first time. We obtain the\ncorrelation length of r_0=2-5 h^(-1) Mpc and bias of b=3-6, and find no\nsignificant boost of clustering amplitude by reionization at z=6.6. The average\nhosting dark halo mass inferred from clustering is 10^10-10^11 Mo, and duty\ncycle of LAE population is roughly ~1% albeit with large uncertainties. The\naverage of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of\n251 +/-16 km s^(-1). We find no large evolution of Lya line profile from z=5.7\nto 6.6, and no anti-correlation between Lya luminosity and line width at z=6.6.\nThe combination of various reionization models and our observational results\nabout the LF, clustering, and line profile indicates that there would exist a\nsmall decrease of IGM's Lya transmission owing to reionization, but that the\nhydrogen IGM is not highly neutral at z=6.6. Our neutral-hydrogen fraction\nconstraint implies that the major reionization process took place at z>~7.\n