Statistics of 207 Lyα Emitters at a Redshift Near 7: Constraints on Reionization and Galaxy Formation Models

Ouchi, Masami; Shimasaku, Kazuhiro; Furusawa, Hisanori; Saito, Tomoki; Yoshida, Makiko; Akiyama, Masayuki; Ono, Yoshiaki; Yamada, Toru; Ota, Kazuaki; Kashikawa, Nobunari; Iye, Masanori; Kodama, Tadayuki; Okamura, Sadanori; Simpson, Chris; Yoshida, Michitoshi

Abstract

We present the Lyα luminosity function (LF), clustering measurements, and Lyα line profiles based on the largest sample to date of 207 Lyα emitters (LAEs) at z = 6.6 on the 1 deg² sky of Subaru/XMM-Newton Deep Survey field. Our z = 6.6 Lyα LF including cosmic variance estimates yields the best-fit Schechter parameters of phi* = 8.5^+3.0 _-2.2 × 10^-4 Mpc^-3 and L*_Lyα = 4.4^+0.6 _-0.6 × 10⁴² erg s^-1 with a fixed α = -1.5, and indicates a decrease from z = 5.7 at the gsim90% confidence level. However, this decrease is not large, only sime30% in Lyα 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 ^-1 ₁₀₀ 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 10¹⁰-10¹¹ M _sun, and a 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 the Lyα line profile from z = 5.7 to 6.6, and no anti-correlation between Lyα 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) Lyα 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.

ADS Listing