Statistics of 207 lyα emitters at a redshift near 7: Constraints on reionization and galaxy formation models

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

Research output: Contribution to journalArticlepeer-review

536 Citations (Scopus)


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 φ* = 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≳90% confidence level. However, this decrease is not large, only ≃30% 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 r0 = 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 1010-1011M⊙, 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.

Original languageEnglish
Pages (from-to)869-894
Number of pages26
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2010 Nov 1


  • Cosmology
  • First stars-galaxies
  • Formation-galaxies
  • High-redshift-galaxies
  • Luminosity function
  • Mass function
  • Observations-dark ages
  • Reionization


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