The end of the reionization epoch probed by Lyα emitters at z = 6.5 in the subaru deep field

Nobunari Kashikawa, Kazuhiro Shimasaku, Matthew A. Malkan, Mamoru Doi, Yuichi Matsuda, Masami Ouchi, Yoshiaki Taniguchi, Chun Ly, Tohru Nagao, Masanori Iye, Kentaro Motohara, Takashi Murayama, Kouji Murozono, Kyoji Nariai, Kouji Ohta, Sadanori Okamura, Toshiyuki Sasaki, Yasuhiro Shioya, Masayuki Umemura

Research output: Contribution to journalArticlepeer-review

351 Citations (Scopus)


We report an extensive search for Lyα emitters (LAEs) at z = 6.5 in the Subaru Deep Field. Subsequent spectroscopy with Subaru and Keck identified eight more LAEs, giving a total of 17 spectroscopically confirmed LAEs at z = 6.5. Based on this spectroscopic sample of 17, complemented by a photometric sample of 58 LAEs, we have derived a more accurate Lyα luminosity function of LAEs at z = 6.5, which reveals an apparent deficit at the bright end of ∼0.75 mag fainter L*, compared with that observed at z = 5.7. The difference in the LAE luminosity functions between z = 5.7 and 6.5 is significant at the 3 σ level, which is reduced to 2 σ when cosmic variance is taken into account. This result may imply that the reionization of the universe has not been completed at z = 6.5. We found that the spatial distribution of LAEs at z = 6.5 was homogeneous over the field. We discuss the implications of these results for the reionization of the universe.

Original languageEnglish
Pages (from-to)7-22
Number of pages16
JournalAstrophysical Journal
Issue number1 I
Publication statusPublished - 2006 Sept 1


  • Cosmology: observations
  • Early universe
  • Galaxies: formation
  • Galaxies: high-redshift


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