SILVERRUSH. V. Census of Lyα, [O III] λ5007, Hα, and [C II] 158 μm Line Emission with ∼1000 LAEs at z = 4.9-7.0 Revealed with Subaru/HSC

June 2018 • 2018ApJ...859...84H

Authors • Harikane, Yuichi • Ouchi, Masami • Shibuya, Takatoshi • Kojima, Takashi • Zhang, Haibin • Itoh, Ryohei • Ono, Yoshiaki • Higuchi, Ryo • Inoue, Akio K. • Chevallard, Jacopo • Capak, Peter L. • Nagao, Tohru • Onodera, Masato • Faisst, Andreas L. • Martin, Crystal L. • Rauch, Michael • Bruzual, Gustavo A. • Charlot, Stephane • Davidzon, Iary • Fujimoto, Seiji • Hilmi, Miftahul • Ilbert, Olivier • Lee, Chien-Hsiu • Matsuoka, Yoshiki • Silverman, John D. • Toft, Sune

Abstract • We investigate Lyα, [O III] λ5007, Hα, and [C II] 158 μm emission from 1124 galaxies at z = 4.9-7.0. Our sample is composed of 1092 Lyα emitters (LAEs) at z = 4.9, 5.7, 6.6, and 7.0 identified by Subaru/Hyper-Suprime-Cam (HSC) narrowband surveys covered by Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) and 34 galaxies at z = 5.148-7.508 with deep ALMA [C II] 158 μm data in the literature. Fluxes of strong rest-frame optical lines of [O III] and Hα (Hβ) are constrained by significant excesses found in the SPLASH 3.6 and 4.5 μm photometry. At z = 4.9, we find that the rest-frame Hα equivalent width and the Lyα escape fraction f _Lyα positively correlate with the rest-frame Lyα equivalent width {EW}}_Lyα }⁰. The {f}_Lyα }{--}{EW}}_Lyα }⁰ correlation is similarly found at z ∼ 0-2, suggesting no evolution of the correlation over z ≃ 0-5. The typical ionizing photon production efficiency of LAEs is log(ξ _ion/[Hz erg^-1]) ≃ 25.5, significantly (60%-100%) higher than those of LBGs at a given UV magnitude. At z = 5.7-7.0, there exists an interesting turnover trend that the [O III]/Hα flux ratio increases in {EW}}_Lyα }⁰≃ 0{--}30 \mathringA and then decreases out to {EW}}_Lyα }⁰≃ 130 \mathringA . We also identify an anticorrelation between a ratio of [C II] luminosity to star formation rate (L _{[C II]}/SFR) and {EW}}_Lyα }⁰ at the >99% confidence level.. We carefully investigate physical origins of the correlations with stellar-synthesis and photoionization models and find that a simple anticorrelation between {EW}}_Lyα }⁰ and metallicity explains self-consistently all of the correlations of Lyα, Hα, [O III]/Hα, and [C II] identified in our study, indicating detections of metal-poor (∼0.03 Z _⊙) galaxies with {EW}}_Lyα }⁰≃ 200 \mathringA .

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Andreas Faisst

Assistant Scientist