A Subaru search for Lyα emitters at redshift 5.7

We present the results of a survey for Lyalpha emitters at zapproximate to5.7 based on optical narrowband (lambda(c)=8150 Angstrom and Deltalambda=120 Angstrom) 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 approximate to720 arcmin(2) and a comoving volume of similar or equal to2x10(5) h(0.7)(-3) Mpc(3). We have found 20 candidate Lyalpha emitters at zapproximate to5.7 with Deltazapproximate to0.1. 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 zapproximate to5.7, similar to1.2x10(-3) h(0.7) M-circle dot yr(-1) Mpc(-3).