Photometric properties of Lyα emitters at z ≈ 4.86 in the cosmos 2 square degree field

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 deg², down to the Lyα line flux of 1.47 × 10 ^-17erg s^-1 cm^-2. We obtain the Lyα luminosity function with a best-fit Schechter parameters of logL ^* = 42.9^+0.5_-0.3 erg s^-1 and φ^* = 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 deg² 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.