A New Constraint on Reionization from the Evolution of the Lyα Luminosity Function at z ∼ 6-7 Probed by a Deep Census of z = 7.0 Lyα Emitter Candidates to 0.3L

Kazuaki Ota, Masanori Iye, Nobunari Kashikawa, Akira Konno, Fumiaki Nakata, Tomonori Totani, Masakazu A.R. Kobayashi, Yoshinobu Fudamoto, Akifumi Seko, Jun Toshikawa, Akie Ichikawa, Takatoshi Shibuya, Masafusa Onoue

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

We detect 20 z = 7.0 Lyα emitter (LAE) candidates to L(Lyα) ∼ 2 × 1042 erg s-1 or 0.3 and in a volume of 6.1 × 105 Mpc3 in the Subaru Deep Field and the Subaru/XMM-Newton Deep Survey field by 82 hr and 37 hr of Subaru Suprime-Cam narrowband NB973 and reddest optical y-band imaging. We compare their Lyα and UV luminosity functions (LFs) and densities and Lyα equivalent widths (EWs) to those of z = 5.7, 6.6, and 7.3 LAEs from previous Suprime-Cam surveys. The Lyα LF (density) rapidly declines by a factor of ×1.5 (1.9) in L(Lyα) at z = 5.7-6.6 (160 Myr), ×1.5 (1.6) at z = 6.6-7.0 (60 Myr) at the faint end, and ×2.0 (3.8) at z = 7.0-7.3 (40 Myr). Also, in addition to the systematic decrease in EW at z = 5.7-6.6 previously found, two-thirds of the z = 7.0 LAEs detected in the UV continuum exhibit lower EWs than the z = 6.6 ones. Moreover, while the UV LF and density do not evolve at z = 5.7-6.6, they modestly decline at z = 6.6-7.0, implying galaxy evolution contributing to the decline of the Lyα LF. Comparison of the z = 7.0 Lyα LF to the one predicted by an LAE evolution model further reveals that galaxy evolution alone cannot explain all of the decline of the Lyα LF. If we attribute the discrepancy to Lyα attenuation by neutral hydrogen, the intergalactic medium transmission of Lyα photons at z = 7.0 would be . It is lower (higher) than the at z = 6.6 (7.3) derived by previous studies, suggesting rapid increase in neutral fraction at z > 6.

Original languageEnglish
Article number85
JournalAstrophysical Journal
Volume844
Issue number1
DOIs
Publication statusPublished - 2017 Jul 20

Keywords

  • cosmology: observations
  • dark ages, reionization, first stars
  • galaxies: formation
  • galaxies: highredshift
  • galaxies: luminosity function, mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'A New Constraint on Reionization from the Evolution of the Lyα Luminosity Function at z ∼ 6-7 Probed by a Deep Census of z = 7.0 Lyα Emitter Candidates to 0.3L <sup>∗</sup>'. Together they form a unique fingerprint.

Cite this