A Subaru Search for Ly Emitters at Redshift 5.7

We present the results of a survey for Lyα emitters at z ≈ 5.7 based on optical narrowband (λ c = 8150 Å and Δλ = 120 Å) and broadband ( B , R C , I C , and z ') observations of the field surrounding the high-redshift quasar SDSSp J104433.04-012522.2 with the 8.2 m Subaru Telescope using the Subaru prime-focus camera, Suprime-Cam. This survey covers a sky area of ≈720 arcmin 2 and a comoving volume of ≃2 × 10 5 h Mpc 3 . We have found 20 candidate Lyα emitters at z ≈ 5.7 with Δ z ≈ 0.1. Two of them have been confirmed as star-forming galaxies at z = 5.655 and z = 5.687 from our follow-up optical spectroscopy. We discuss the star formation properties of the 20 objects from a statistical point of view. Our survey leads to a new estimate of the star formation rate density at z ≈ 5.7, ∼1.2 × 10 -3 h 0.7 M ⊙ yr -1 Mpc -3 .