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

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^0_( Lyα). The f_(Lyα)-EW^0_( Lyα) 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^0_( Lyα) ≃ 0-30 Å and then decreases out to EW^0_( Lyα) ≃ 130 Å. We also identify an anticorrelation between a ratio of [C II] luminosity to star formation rate (L [C II]/SFR) and EW^0_( Lyα) 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^0_( Lyα) 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^0_( Lyα) ≃ 200 Å.

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