Lyα Emitters at z = 5.7 in the Subaru Deep Field

PASJ: Publ. Astron. Soc. Japan , 1–? , c 2008. Astronomical Society of Japan. Lyα Emitters at z = 5.7 in the Subaru Deep Field Kazuhiro Shimasaku, 1,2 Nobunari Kashikawa, 3,4 Mamoru Doi, 5,2 Chun Ly, 6 Matthew A.Malkan, 6 Yuichi Matsuda, 7 Masami Ouchi, 8,‡ Tomoki Hayashino, 9 Masanori Iye, 3,4 Kentaro Motohara, 5 Takashi Murayama, Tohru Nagao, 3,11 Kouji Ohta, 12 Sadanori Okamura, 1,2 Toshiyuki Sasaki, 13 Yasuhiro Shioya, 10 Yoshiaki Taniguchi 10 arXiv:astro-ph/0602614v1 28 Feb 2006 Department of Astronomy, School of Science, The University of Tokyo, Tokyo 113-0033 Email (KS): shimasaku@astron.s. u-tokyo.ac. jp Research Center for the Early Universe, School of Science, The University of Tokyo, Tokyo 113-0033 Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 Institute of Astronomy, School of Science, The University of Tokyo, Mitaka 181-0015 Department of Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1547, USA Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA Research Center for Neutrino Science, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578 Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578, Japan INAF / Osservatorio Astrofisico di Arcetri Largo E. Fermi 5, 50125 Firenze, Italy Kouji Ohta Department of Astronomy, Kyoto University, Kyoto 606-8502 Subaru Telescope, National Astronomical Observatory of Japan, 650 N. A’ohoku Place, Hilo, HI 96720, USA (Received 2005 October 26; accepted 2006 February 27) Abstract We present the properties of Lyα emitters (LAEs) at z = 5.7 in the Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed from narrow-band (NB816) data down to N B816 = 26.0 (AB) in a continuous 725 arcmin 2 area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Lyα luminosity function derived from the photometric sample is reproduced well by a Schechter function with L ⋆ = 7.9 +3.0 erg s −1 and φ ⋆ = 6.3 −2.0 × 10 −4 Mpc −3 for α = −1.5 (fixed) over the whole luminosity range of L ≃ 3 × 10 42 – 3 × 10 43 erg s −1 . We then measure rest-frame Lyα equivalent widths (EWs) for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is W i0 = 233 ˚ A. We infer that 30% – 40% of LAEs at z = 5.7 exceed W i0 = 240 ˚ A. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derive the far-UV luminosity function of LAEs down to M UV ≃ −19.6 using the photometric sample, and compare it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at z ∼ 6 have W i0 ≥ 100 ˚ A, in sharp contrast to lower-z counterparts. Key words: galaxies: evolution — galaxies: high-redshift — galaxies: luminosity function, mass function — galaxies: photometry