1. Probing Reionization & Galaxy Evolution by High-z Lyα Emitters
z=6.96 LAE
Kazuaki Ota Cosmic Radiation Lab. RIKEN Institute of Physical and Chemical Research

2. Outline When did reionization end? I. Goal: to address the question,
II. Approach: Lyα Emitters
III. Result
IV. Conclusion
V. Upcoming Projects

3. Outline When did reionization end? I. Goal: to address the question,
II. Approach: Lyα Emitters
III. Result
IV. Conclusion
V. Upcoming Projects

4. When did reionization end?
GP trough
quasars
Fan et al. 2006
neutral fraction
XHI ~ 1 – 4%
z=6.3
WMAP (CMB)
Dunkley et al. 2008
zreion=11.0±1.4
zreion　> 6.7 (3σ limit)
γ-ray burst
Totani et al. 2006
neutral fraction
0< XHI < 17 – 60%

5. Reionization Scenario: Late vs. Early
Neutral Fraction XHI
Redshift z
Fan et al.2006 ARAA

6. Reionization might have ended at z~6.
Our Result: LAEs support late reionization
Neutral Fraction XHI
z=7 z=6.6 Lyα Emitters (LAEs)
Reionization might have ended at z~6.
Redshift z
Fan et al.2006 ARAA

7. Outline When did reionization end? I. Goal: to address the question,
II. Approach: Lyα Emitters
III. Result
IV. Conclusion
V. Upcoming Projects

8. Reionization Probe： z~6 Quasars Neutral Fraction1 – 4%
Fan et al. 2002
Reionization Probe：　 z~6 Quasars Neutral Fraction1 – 4%
GP trough
z=5.7
z=6.6
z=7
Lyα emitters (LAEs)
If NF increases beyond z~6, observed LAE number density could decrease beyond z~6.
Iye et al. 2006

9. Narrowband Filters to Detect Lyα
Filter Response
z=5.7Lyα
z=6.6
z=7 LAE
Skylines
z=7
　　　Wavelength (A)

10. Sample Selection: NB excess Taniguchi et al.2005 Kashikawa et al.2006
z=5.7 LAEs
z=6.6 LAEs
Shimasaku et al.2006
Taniguchi et al.2005 Kashikawa et al.2006

11. Sample Selection of z=7LAEs
i’ – z’ [mag]
z’ – NB973 [mag]
3:z=6.6LAE 1
Detected in only NB973 2
Model z=7 LAE
Ota et al.2008

12. Spectroscopic confirmation
Kashikawa et al.2006 z=6.6 LAEs 89% complete
Shimasaku et al.2006 z=5.7 LAEs 86% complete
Iye, Ota et al.2006 z=7 LAE

13. Target Sky Region & Samples
3σ, 2” aper. Limit. Mag. B ≤ V ≤ 　 　 R ≤ i’ ≤ z’ ≤ 26.62
NB816 ≤ (z=5.7)
NB921 ≤ (z=6.6)
NB973 ≤ (z=7.0)
876 arcmin2
Subaru Deep Field
Suprime-Cam
SDF Latest LAE Samples
　　　　 Image　Spec.　 z= Shimasaku et al z= Kashikawa et al z= 　 Ota et al. 2008

14. Outline When did reionization end? I. Goal: to address the question,
II. Approach: Lyα Emitters
III. Result
IV. Conclusion
V. Upcoming Projrcts

15. Comparison of z<6 & z>6 LAE’s Lyα Luminosity Function (LF)
Did reionization end at z~6?
Does HI increase beyond z=6?
Comparison of z<6 & z>6 LAE’s
Lyα Luminosity Function (LF)
Increase in HI
galaxy evolution
LAE evolution model

16. Lyα LF（Observed） Number density log[n(>L) Mpc-3]
z=5.7Phot■ z=6.6Phot● z=6.6Spec▲ z=7.0Spec◆
z=7LAE detection limit
Number density log[n(>L) Mpc-3]
Decline in n(>L) ・galaxy evolution? ・increase in HI? ・both?
Lyα Luminosity log[L(Lyα) erg/s]

17. IGM transmission to Lyα photons
A LAE Evolution Model (Kobayashi et al.2007)
Observed Lyα luminosity
IGM transmission to Lyα photons
0 ≤ TLyα ≤ 1
IGM
Lyα luminosity emitted from a galaxy
fesc =0
Lyc
Lyα emitters
Quiescent galaxy
Starburst galaxy
Lyα escape fraction
0.8
outflow + dust model

18. Lyα LF（Model vs. Observation）
　LAE evolution model 　　 (Kobayashi et al.2007)
TLyα=1
IGM
galaxy evol.
Number density log[n(>L) Mpc-3]
Increase in HI
TLyα z=6.6: 0.62–0.78
IGM
Lyα Luminosity log[L(Lyα) erg/s]

19. Lyα LF（Model vs. Observation）
　LAE evolution model 　　 (Kobayashi et al.2007)
TLyα=1
IGM
galaxy evol.
Number density log[n(>L) Mpc-3]
Increase in HI
TLyα z=7.0: 0.40–0.64
IGM
Lyα Luminosity log[L(Lyα) erg/s]

20. Neutral Fraction z=6.6 24–36% z=7.0 32–64%
IGM transmission to Lyα photons: TLyα
z=6.6: 0.62–0.78
z=7.0: 0.40–0.64
Neutral Fraction z= –36% z= –64%
IGM
Lyα line attenuation: Model of Santos（2004）
Neutral Fraction
wavelength(A)
Flux
IGM
TLyα

21. z~3-5 z=5.7 z=6.5 z=7 Gal. evol. reionization
Model prediction Kobayashi 07
reionization
z=6.5
z=7
Ouchi 08
Shimasaku 06
Dawson 07
Kashikawa 06
van Breukelen 05
Ota 08

22. Reionization History Neutral Fraction XHI Redshift z
z=7 z=6.6 Lyα Emitters
Redshift z
Fan et al.2006 ARAA

23. LAEs support late reionization. Reionization might have ended at z~6.
Conclusion
When did reionization end?
NOTE:
Estimation of XHI is model dependent.
z=7 LAE survey is shallow.
We surveyed only one sky field.
LAEs support late reionization.
Reionization might have ended at z~6.

24. Outline When did reionization complete?
I. Goal: to address the question,
When did reionization complete?
II. Approach: Lyα Emitters
III. Result
IV. Conclusion
V. Upcoming Projects

25. Upcoming Projects New Filter + New CCDs
Filter Response
Wavelength (A)
NB1005 filter z~7.3 LAE center=10050A FWHM=210A
NB1005
34’x27’ Suprime-Cam
Red-sensitive CCDs for Suprime-Cam 1μm ~ 0.422

26. 876 arcmin2 Suprime-Cam 1 pointing
Upcoming Project (1)
Deepen z=7 Image NB973=24.9  25.4
Obtain z=7.3 Image NB1005=25.0 or deeper
Improved samples z=7 LAEs z=7.3 LAEs
Subaru Deep Field
876 arcmin2 Suprime-Cam 1 pointing

27. Upcoming Project (2)
Subaru/XMM-Newton Deep Survey（SXDS） ~1.3 degree2 (Suprime-Cam 5 pointings)
Samples: z=5.7 LAEs 5 fields z=6.6 LAEs 5 fields (Ouchi et al.) z=7 LAEs field z=7.3 LAEs 1 field (Observation in this Oct. & Nov.)

28. UV LF of LAEs at z=5.7 – 7