Silverrush. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼ 1,300 LAEs on the 14 − 21 deg2 sky

Akira Konno, Masami Ouchi, Takatoshi Shibuya, O. N.O. Yoshiaki, Kazuhiro Shimasaku, Yoshiaki Taniguchi, Tohru Nagao, Masakazu A.R. Kobayashi, Masaru Kajisawa, Nobunari Kashikawa, Akio K. Inoue, Masamune Oguri, Hisanori Furusawa, Tomotsugu Goto, Yuichi Harikane, Ryo Higuchi, Yutaka Komiyama, Haruka Kusakabe, Satoshi Miyazaki, Kimihiko NakajimaShiang Yu Wang

Research output: Contribution to journalArticlepeer-review


We present the Lyα luminosity functions (LFs) at z = 5.7 and 6.6 derived from a new large sample of 1,266 Lyα emitters (LAEs) identified in total areas of 14 and 21 deg2, respectively, based on the early narrowband data of the Subaru/Hyper Suprime-Cam (HSC) survey. Together with careful Monte-Carlo simulations that account for the incompleteness of the LAE selection and the flux estimate systematics in the narrowband imaging, we have determined the Lyα LFs with the unprecedentedly small statistical and systematic uncertainties in a wide Lyα luminosity range of 1042.8−43.8 erg s−1. We obtain the best-fit Schechter parameters of LLyα = 1.6+2−0..26 (1.7+0−0..37) × 1043 erg s−1, φLyα = 0.85+1−0..8777 (0.47+1−0..4444) × 10−4 Mpc−3, and α = −2.6+0−0..64 (−2.5+0−0..55) at z = 5.7 (6.6). We confirm that our best-estimate Lyα LFs are consistent with the majority of the previous studies, but find that our Lyα LFs do not agree with the high number densities of LAEs recently claimed by Matthee/Santos et al.’s studies that may overcorrect the incompleteness and the flux systematics. Our Lyα LFs at z = 5.7 and 6.6 show an indication that the faint-end slope is very steep (α ≃ −2.5), although it is also possible that the bright-end LF results are enhanced by systematic effects such as the contribution from AGNs, blended merging galaxies, and/or large ionized bubbles around bright LAEs. Comparing our Lyα LF measurements with four independent reionization models, we estimate the neutral hydrogen fraction of the IGM to be xHI = 0.3 ± 0.2 at z = 6.6 that is consistent with the small Thomson scattering optical depth obtained by Planck 2016.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - 2017 May 2
Externally publishedYes


  • Cosmology: dark ages
  • Cosmology: observations
  • First stars
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: luminosity function
  • Mass function
  • Reionization

ASJC Scopus subject areas

  • General

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