Photometric Properties of Lyα Emitters at z ≈ 4.86 in the COSMOS 2 Square Degree Field

Abstract

We present results of a survey for Lyα emitters at z ≈ 4.86 based on optical narrowband (λ_c = 7126 Å, Δλ = 73 Å) and broadband (B, V, r', i', and z') observations of the Cosmic Evolution Survey field using Suprime-Cam on the Subaru Telescope. We find 79 Lyα emitter (LAE) candidates at z ≈ 4.86 over a contiguous survey area of 1.83 deg^2, down to the Lyα line flux of 1.47 × 10^(–17) erg s^(-1) cm^(–2). We obtain the Lyα luminosity function with a best-fit Schechter parameters of log L* = 42.9^(+0.5)_(–0.3) erg s^(-1) and Ф* = 1.2^(+8.0)_(–1.1) × 10^(–4) Mpc^(-3) for α = –1.5 (fixed). The two-point correlation function for our LAE sample is ξ(r) = (r/4.4^(+5.7)_(–2.9) Mpc)^(–1.90±0.22). In order to investigate the field-to-field variations of the properties of Lyα emitters, we divide the survey area into nine tiles of 0°.5 × 0°.5 each. We find that the number density varies with a factor of ≃ 2 from field to field with high statistical significance. However, we find no significant field-to-field variance when we divide the field into four tiles with 0°.7 × 0°.7 each. We conclude that at least 0.5 deg^2 survey area is required to derive averaged properties of LAEs at z ~ 5, and our survey field is wide enough to overcome the cosmic variance.

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