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The Reionization and Galaxy Evolution Probed by z=7 Lyα Emitters

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

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The Reionization and Galaxy Evolution Probed by z=7 Lyα Emitters

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  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 OtaCosmic 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~14 z~6

  3. 876 arcmin2 Narrowband filter NB973 to detectz=6.9-7Lya(λc=9755Å, FWHM=200Å) Subaru Deep Field Suprime-Cam B ≤ 28.45V ≤ 27.74R ≤ 27.80, NB816 ≤ 26.63i’ ≤ 27.43, NB921 ≤ 26.54z’ ≤ 26.62, NB973 ≤ 24.90 (5σ) 34’×27’ Field of View ●16,17 March 2005 ● Seeing 0.”4-0.”9●15 hours integration ●Volume: 3.2×105 Mpc3

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

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

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

  7. 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.

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

  9. Galaxy evolutionreionization Semi-analytic model (kobayashi et al.2006) Galaxy evolutionreionization 7.0 5.7 6.6 Redshift

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

  11. Neutral Fraction Fan et al.2006 ARAA

  12. Neutral Fraction Lyα EmittersThis Study Fan et al.2006 ARAA

  13. 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.

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

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

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

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