1. Deep Survey of z=7 Lyα Emitters with the new red-sensitive CCDs on Subaru / Suprime-Cam Kazuaki Ota Cosmic Radiation Laboratory RIKEN M. Iye, N. Kashikawa (NAOJ), M. Ouchi (Carnegie), K. Shimasaku (Univ. of Tokyo), T. Totani (Kyoto Univ.), M.A.R. Kobayashi, T. Morokuma (NAOJ), M. Nagashima (Nagasaki Univ.), H. Furusawa, T. Hattori (SubaruTelescope), N. Kodaka, A. Harayama (Saitama Univ.) Reionization @ Ringberg

2. Outline I. Background & Motivation (1) Reionization probed by Lyα emitters at z ≿ 6 (2) Weaknesses in the previous z=7 Lyα emitter survey II. Solution: - New deeper z=7 survey in SXDS Field III. Result: - Deeper Lyα LF and Constraint on X HI IV. Conclusion

3. Outline I. Background & Motivation (1) Reionization probed by Lyα emitters at z ≿ 6 (2) Weaknesses in the previous z=7 Lyα emitter survey II. Solution: - New deeper z=7 survey in SXDS Field III. Result: - Deeper Lyα LF and Constraint on X HI IV. Conclusion

4. Fan et al.2006 Redshift z Neutral Fraction X HI z=7 z=6.6 Lyα Emitters Neutral Fraction vs Redshift z=6.3, 6.7

5. Reionization Probed by Lyα emitters: Lyα LF Number & Lyα luminosity density decrease. n(z=6.6)/n(z=5.7)=0.24 n(z=7.0)/n(z=6.6)=0.17 to L(Lya) > 10 43 erg/s Lyα LF declines. Subaru Deep Field Project Subaru Telescope Suprime-Cam

6. 3 weakneses in the previous z=7 survey Subaru Deep Field 876 arcmin 2 (1) Depth was shallow. (2) Sample is small. (3) Only one sky field was surveyed. L(Lyα) > 10 43 erg/s Only 1 Lyα emitter

7. Outline I. Background & Motivation (1) Reionization probed by Lyα emitters at z ≿ 6 (2) Weaknesses in the previous z=7 Lyα emitter survey II. Solution: - New deeper z=7 survey in SXDS Field III. Result: - Deeper Lyα LF and Constraint on X HI IV. Conclusion

8. Wavelenght (A) New fully depleted CCDs on Subaru / Suprime-Cam More sensitive to 0.9 – 1 μm light Transmission, QE, flux >2 x more sensitive to z=7 Lyα

9. Target Sky Region Subaru/XMM-Newton Deep Survey Field （ SXDS ） Spitzer UKIDSS-UDS Oct, Nov 2008 Subaru This Work 13 hours imaging NB973 = 25.4 (5σ) (previously, 24.9)

10. z=7 Lyα Filter Response Wavelength( Å ) NB973 Narrowband filter to detect z=7 Lyα emitters λc=9755 Å⊿ λ=200 Å

11. New z=7 Lyα emitter candidates No detection (< 3σ) NB973 ≤ 25.4 (5σ) B V R i’ NB816 z’ NB921 NB973 Equivalently, z’ – NB973 > 1 ~

12. Remove spurious & transient objects using images taken in different months Color Selection Visual Inspection 10 z=7 Lyα emitter candidates （ tentative) #Candidates ≤ 10

13. Outline I. Background & Motivation (1) Reionization probed by Lyα emitters at z ≿ 6 (2) Weaknesses in the previous z=7 Lyα emitter survey II. Solution: - New deeper z=7 survey in SXDS Field III. Result: - Deeper Lyα LF and Constraint on X HI IV. Conclusion

14. Lyα Luminosity Function Assumption (1): F(Lyα) = F(NB filter) x HI =0.0 x HI =0.4 x HI =0.6 Attenuated Schechter LFs (Santos 2004) Neutral Fraction z=7.0 ~49% Observed Densities n Lyα : 3.9x10 -5 Mpc -3 ρ Lyα : 4.7x10 38 erg/s/Mpc -3 Predicted Densities when x HI =0 ( Kobayashi et al. 2007 LAE evolution Model) n Lyα : 1.1x10 -4 Mpc -3 ρ Lyα : 9.5x10 38 erg/s/Mpc -3 >6x10 42 erg/s ■ △ z=5.7 ●▲ z=6.6 ◆ z=7.0

15. NB973 Filter Total FluxSpectrum Fraction of Lyα flux in NB filter flux F(Lyα) ~ 0.7 x F(NB973) F(UV) F(NB973) = F(Lya) + F(UV) 70% F(Lyα) 30% F(Lyα)

16. Lyα Luminosity Function: Assumption (2): F(Lyα) = 0.7 x F(NB973) x HI =0.0 x HI =0.4 x HI =0.6 Attenuated Schechter LFs (Santos 2004) Neutral Fraction z=7.0 ~66% Observed Densities n Lyα : 3.9x10 -5 Mpc -3 ρ Lyα : 4.7x10 38 erg/s/Mpc -3 Predicted Densities when x HI =0 ( Kobayashi et al. 2007 LAE evolution Model) n Lyα : 1.8x10 -4 Mpc -3 ρ Lyα : 1.2x10 39 erg/s/Mpc -3 >4.2x10 42 erg/s ■ △ z=5.7 ●▲ z=6.6 ◆ z=7.0

17. Fan et al.2006 Redshift z Neutral Fraction vs Redshift Neutral Fraction X HI z=7 z=6.6 Lyα Emitters z=6.3, 6.7

18. Outline I. Background & Motivation (1) Reionization probed by Lyα emitters at z ≿ 6 (2) Weaknesses in the previous z=7 Lyα emitter survey II. Solution: - New deeper z=7 survey in SXDS Field III. Result: - Deeper Lyα LF and Constraint on X HI IV. Conclusion

19. Conclusion (1) Number & Lyα luminosity densities of Lyα emitters decrease from z=5.7 of Lyα emitters decrease from z=5.7 and 6.6 to z=7. and 6.6 to z=7. (2) Neutral Fraction at z=7 is X HI 0.49 – 0.66. X HI ≿ 0.49 – 0.66. (3) Reionization seems not to be complete at z=7. complete at z=7. Improved statistics & depth, Observed different sky field

20. Wavelenght (A) We are now challenging z=7.3 Lyα Transmission, QE, flux Final survey that can be done by Suprime-Cam + New CCDs