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 *}

Journal Article · Thu Jul 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA7A0A· OSTI ID:22875989

Ota, Kazuaki ^[1]; Iye, Masanori; Kashikawa, Nobunari; Onoue, Masafusa ^[2]; Konno, Akira; Totani, Tomonori ^[3]; Nakata, Fumiaki ^[4]; Kobayashi, Masakazu A. R. ^[5]; Fudamoto, Yoshinobu ^[6]; Seko, Akifumi ^[7]; Toshikawa, Jun; Shibuya, Takatoshi ^[8]; Ichikawa, Akie ^[9]

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1. Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
2. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 (Japan)
3. Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)
4. Subaru Telescope, 650 North A’ohoku Place, Hilo, HI 96720 (United States)
5. Faculty of Natural Sciences, National Institute of Technology, Kure College, 2-2-11 Agaminami, Kure, Hiroshima 737-8506 (Japan)
6. Observatoire de Genéve, Chemin des Maillettes 51, CH-1290 Versoix (Switzerland)
7. Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)
8. Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)
9. Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan)

We detect 20 z = 7.0 Lyα emitter (LAE) candidates to L(Lyα) ∼ 2 × 10{sup 42} erg s{sup −1} or 0.3 L{sub z=7}{sup ∗} and in a volume of 6.1 × 10{sup 5} Mpc{sup 3} 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 T{sub Lyα}{sup IGM}⩽0.6--0.7. It is lower (higher) than the T{sub Lyα}{sup IGM} at z = 6.6 (7.3) derived by previous studies, suggesting rapid increase in neutral fraction at z > 6.

• OSTI ID: 22875989
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 844; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
COSMOLOGY
DENSITY
GALACTIC EVOLUTION
GALAXIES
HYDROGEN
LUMINOSITY
LYMAN LINES