1. The Reionization and Galaxy Evolution Probed by z=7 Lyα Emitters Ota, 2007, PhD Thesis, Univ. Tokyo Iye, Ota, Kashikawa et al. 2006, Nature, 443, 186 Ota et al. 2007, submitted to ApJ (arXiv:0707.1561) Kazuaki Ota Cosmic Radiation Laboratory, RIKEN Masanori Iye, Nobunari Kashikawa, Kazuhiro Shimasaku, Masakazu Kobayashi, Tomonori Totani, Masahiro Nagashima, Tomoki Morokuma, Hisanori Furusawa, Takashi Hattori, Yuichi Matsuda, Tetsuya Hashimoto, Masami Ouchi

2. z~6 z~14

4. Subaru Deep Field Suprime-Cam Narrowband filter NB973 to detect z=6.9-7 Lya (λc=9755 Å, FWHM=200 Å ) B ≤ 28.45 V ≤ 27.74 R ≤ 27.80, NB816 ≤ 26.63 i’ ≤ 27.43, NB921 ≤ 26.54 z’ ≤ 26.62, NB973 ≤ 24.90 (5σ) 876 arcmin 2 34’×27’ Field of View ●16,17 March 2005 ● Seeing 0.”4-0.”9 ●15 hours integration ●Volume: 3.2×10 5 Mpc 3

5. Two z=7 LAE Candidates < 3σ NB973 < 24.9 (5σ)

6. Subaru ＋ FOCAS May, June 2005, April 2006 １００００ Å ８３００Å slits W ： 0.″8 L ： 8 ‐ 15″ ・ 175 lines mm -1 + z’ filter ・ R ~ 1600 ・ Dispersion = 0.98 Å pixel -1 Spectroscopy

7. 5.5hr exp. S/N=5.5 SFR(Lyα) ～ 10M ʘ yr -1 A Galaxy was forming just 750Myr after the Big Bang! ID of Candidate1: z=6.96LAE Red line ： z=6.96 LAE Blue line ： Composite of 12 z=6.6 LAEs

8. IOK- ２ ID of Candidate2: Noise? 11 hours integration time Spectroscopic limit reaches Lya line flux estimated from NB973 photometry However, no signal was detected. Maybe, it is noise.

9. z=5.7 z=6.6 z=7 Quasar GP trough neutral fraction 1-4% z>6 → If HI increases rapidly, it attenuates Lya photons. → Observed LAE number density decreases? 3 Lya emitter samples

10. 5.7 Redshift 6.6 7.0 Galaxy evolution reionization Semi-analytic model (kobayashi et al.2006)

11. neutral fraction @z=7.0: 32-64% @z=6.6: 24-36% Santos （ 2004 ） neutral fraction L(Lyα) obs / L(Lyα) intrinsic wavelength （Å） φλ（Å）φλ（Å） L(Lya) observed L(Lya) intrinsic

12. Fan et al.2006 ARAA Neutral Fraction

13. Fan et al.2006 ARAA Lyα Emitters This Study Neutral Fraction

14. Conclusion Q1. Can we still find objects at z>6.6 ？ YES. At least one galaxy at z=7. We do not know about z>7. Q2. How was the reionization at z>6? Probably YES. Our result is consistent with theory and other observations. YES. At least one galaxy at z=7. We do not know about z>7. Neutral fraction rapidly increases, being consistent with theory and other observations.

15. i’ – z’ [mag] z’ – NB973 [mag] 1 2 Detected in only NB973 3:z=6.6LAE Model z=7 LAE

16. i’ – z’ [mag] z’ – NB973 [mag] 1 2 Detected in only NB973 3:z=6.6LAE Model z=7 LAE

17. Lya line Luminosity Function Shimasaku+06 Kashikawa+06 Kobayashi+07