Probing Reionization & Galaxy Evolution by High-z Lyα Emitters

Kazuaki OtaCosmic Radiation Lab.

RIKEN Institute of Physical and

Chemical Research

Probing Reionization & Galaxy Evolution by High-z Lyα Emitters

z=6.96 LAE

OutlineOutline

I. Goal: to address the question,I. Goal: to address the question,

When did reionizationWhen did reionization end?end?

II. Approach: LyαII. Approach: Lyα Emitters Emitters

III. ResultIII. Result

IV. ConclusionIV. Conclusion

V. Upcoming ProjectsV. Upcoming Projects

OutlineOutline

I. Goal: to address the question,I. Goal: to address the question,

When did reionizationWhen did reionization end?end?

II. Approach: LyαII. Approach: Lyα Emitters Emitters

III. ResultIII. Result

IV. ConclusionIV. Conclusion

V. Upcoming ProjectsV. Upcoming Projects

WMAP (CMB)WMAP (CMB)Dunkley et al. 2008

zreion=11.0±1.4zreion 　 > 6.7 (3σ

limit)

When did reionization end?

γ-ray burstγ-ray burstTotani et al. 2006neutral fraction0< XHI < 17 – 60%

GP trough

quasarsquasarsFan et al. 2006neutral fractionXHI ~ 1 – 4%

z=6.3

z~6.2

Fan et al.2006 ARAA

Neu

tral

Fra

ctio

n X

HI

Redshift z

Reionization Scenario: Late vs. Early

Fan et al.2006 ARAARedshift z

Neu

tral

Fra

ctio

n X

HI

z=7z=6.6Lyα Emitters(LAEs)

Our Result: LAEs support late reionization

Reionization might have ended at z~6.Reionization might have ended at z~6.

OutlineOutline

I. Goal: to address the question,

When did reionizationWhen did reionization end?end?

II. Approach: LyαII. Approach: Lyα Emitters Emitters

III. ResultIII. Result

IV. ConclusionIV. Conclusion

V. Upcoming ProjectsV. Upcoming Projects

z=5.7z=6.6 z=7

If NF increases beyond z~6,observed LAE number density could decrease beyond z~6.

Fan et al. 2002

GP troughReionization Probe ：　z~6 Quasars Neutral Fraction1 – 4%

Iye et al. 2006

Lyα emitters (LAEs)

Filt

er R

esp

on

se

　　　 Wavelength (A)

Narrowband Filters to Detect LyNarrowband Filters to Detect Lyα

z=5.7Lyα

z=6.6

z=7LAE

z=7

Skylines

Sample Selection: NB excessSample Selection: NB excess

z=5.7 LAEs z=6.6 LAEs

Shimasaku et al.2006 Taniguchi et al.2005Kashikawa et al.2006

Sample Selection of z=7LAEsSample Selection of z=7LAEs

i’ – z’ [mag]

z’ –

NB

973

[mag

] 12

Detected in only NB973

3:z=6.6LAE

Model z=7 LAE

Ota et al.2008

Spectroscopic confirmationSpectroscopic confirmation

Shimasaku et al.2006z=5.7 LAEs 86% complete

Kashikawa et al.2006z=6.6 LAEs 89% complete

Iye, Ota et al.2006z=7 LAE

Subaru Deep Field Suprime-Cam876 arcmin2

SDF Latest LAE Samples　 　 　 　 　　 Image 　 Spec. 　z=5.7 89 34 Shimasaku et al. 2006z=6.6 58 17 Kashikawa et al. 2006z=7.0 2 1 　 　　 Ota et al. 2008

Target Sky Region & SamplesTarget Sky Region & Samples3σ, 2” aper. Limit. Mag.　　B ≤ 28.45 V ≤ 27.74 　 　　　 R ≤ 27.80 i’ ≤ 27.43 z’ ≤ 26.62 NB816 ≤ 26.63 (z=5.7) NB921 ≤ 26.54 (z=6.6) NB973 ≤ 25.47 (z=7.0)

OutlineOutline

I. Goal: to address the question,

When did reionizationWhen did reionization end?end?

II. Approach: Lyα Emitters

III. ResultIII. Result

IV. ConclusionIV. Conclusion

V. Upcoming ProjrctsV. Upcoming Projrcts

Did reionization end at z~6?

Does HI increase beyond z=6?

Comparison of z<6 & z>6 LAE’s Comparison of z<6 & z>6 LAE’s Lyα Luminosity Function (LF)Lyα Luminosity Function (LF)

LAE evolution modelLAE evolution model

Increase in HIIncrease in HIgalaxy evolutiongalaxy evolution

Lyα LF （ Observed ）z=5.7Phot■z=6.6Phot●z=6.6Spec▲z=7.0Spec◆

Lyα Luminosity log[L(Lyα) erg/s]

Num

ber

dens

ity lo

g[n(

>L)

Mpc

-3]

Decline in n(>L) ・ galaxy evolution?・ increase in HI?・ both?

z=7LAEdetectionlimit

Starburst galaxy

Quiescent galaxy

A LAE Evolution ModelA LAE Evolution Model (Kobayashi et al.2007)(Kobayashi et al.2007)

Lyα emitters

IGM transmission to Lyα photons

Lyα escape fraction

Observed Lyα luminosity

0 ≤　TLyα ≤　1IGM

fesc =0Lyc Lyα luminosity emitted from a galaxy

outflow + dustmodel

0.8

Lyα LF （ Model vs. Observation ）

Lyα Luminosity log[L(Lyα) erg/s]

　 LAE evolution model　　 　 (Kobayashi et al.2007)

galaxy evol.

Increase in HI

Num

ber

dens

ity lo

g[n(

>L)

Mpc

-3]

TLyα z=6.6: 0.62–0.78 IGM

TLyα=1IGM

Lyα LF （ Model vs. Observation ）

Lyα Luminosity log[L(Lyα) erg/s]

　 LAE evolution model　　 　 (Kobayashi et al.2007)

galaxy evol.

Num

ber

dens

ity lo

g[n(

>L)

Mpc

-3]

TLyα z=7.0: 0.40–0.64IGM

TLyα=1IGM

Increase in HI

Lyα line attenuation: Model of Santos （ 2004 ）

Neutral Fractionwavelength(A)

Flu

xIGM transmission to Lyα photons: TLyα

z=6.6: 0.62–0.78 z=7.0: 0.40–0.64

Neutral Fraction z=6.6 24–36% z=7.0 32–64%

TL

yα

IGM

IGM

z=5.7

z=6.5

z=7

Ota 08Kashikawa 06

Shimasaku 06 Ouchi 08

van Breukelen 05

Dawson 07

Gal. evol.

z~3-5

Model predictionKobayashi 07

reionization

Fan et al.2006 ARAARedshift z

Reionization HistoryN

eutr

al F

ract

ion

XH

I

z=7z=6.6Lyα Emitters

ConclusionConclusion

When did reionizationWhen did reionization end?end?

NOTE:NOTE:• Estimation of XEstimation of XHIHI is model dependent. is model dependent.• z=7 LAE survey is shallow.z=7 LAE survey is shallow.• We surveyed only one sky field.We surveyed only one sky field.

LAEs support late reionization.LAEs support late reionization.Reionization might have ended at Reionization might have ended at

z~6.z~6.

OutlineOutline

I. Goal: to address the question,I. Goal: to address the question,

When did reionizationWhen did reionization complete?complete?

II. Approach: LyαII. Approach: Lyα Emitters Emitters

III. ResultIII. Result

IV. ConclusionIV. Conclusion

V. Upcoming ProjectsV. Upcoming Projects

NB1005 filterNB1005 filter z~7.3 LAE z~7.3 LAE center=10050Acenter=10050AFWHM=210AFWHM=210A

Upcoming ProjectsUpcoming ProjectsNew Filter + New CCDsNew Filter + New CCDs

Fil

ter

Res

po

nse

Wavelength (A)

Red-sensitive CCDs Red-sensitive CCDs for Suprime-Camfor Suprime-CamQEQE @ 1μm ~ 0.422@ 1μm ~ 0.422

34’x27’ Suprime-Cam

NB1005

Upcoming Project (1)Upcoming Project (1)

Subaru Deep Field

Deepen z=7 ImageNB973=24.9 25.4

876 arcmin2

Suprime-Cam 1 pointing

Improved samples z=7 LAEs z=7.3 LAEs

Obtain z=7.3 ImageNB1005=25.0 or deeper

Upcoming Project (2)Upcoming Project (2)

Samples:z=5.7 LAEs 5 fieldsz=6.6 LAEs 5 fields(Ouchi et al.)

z=7 LAEs 1 fieldz=7 LAEs 1 fieldz=7.3 LAEs 1 fieldz=7.3 LAEs 1 field(Observation in this Oct. & Nov.) (Observation in this Oct. & Nov.)

Subaru/XMM-Newton Deep

Survey （ SXDS ）~1.3 degree2

(Suprime-Cam 5 pointings)

UV LF of LAEs at z=5.7 – 7 UV LF of LAEs at z=5.7 – 7