A Search for Lymanα Emitters at Redshift 3.7

We present the results of a survey for emission-line objects based on optical intermediate-band (λc = 5736 Å and ∆λ = 280 Å) and broad-band (B, V , R, and i) observations of the Subaru/XMM-Newton Deep Field on the 8.2 m Subaru telescope with the Subaru Prime Focus Camera, Suprime-Cam. All the data were obtained during the guaranteed time observations of the Suprime-Cam instrument. The intermediate-band image covered a sky area with 10.62 ×12.40 ≈ 132 arcmin in the Subaru/XMMNewton Deep Field (Ouchi et al.). Using this image, we have found 23 emission-line sources whose observed emission-line equivalent widths are greater than 250 Å. Their optical multicolor properties indicate that six emission-line sources are Lyα emitters at z ≈ 3.7 (∆z ≈ 0.22). They are either intense starburst galaxies or active galactic nuclei like quasars at z ≈ 3.7. Two more emission-line sources may also be Lyα emitters at z ≈ 3.7 although their multicolor properties are marginal. Among the remaining 15 emission-line objects, eight objects appear strong emission-line galaxies at lower redshift; e.g., [O ii] λ3727 emitters at z ≈ 0.54, Hβ at z ≈ 0.18, or [O iii]λ5007 emitters at z ≈ 0.15. The remaining seven objects are unclassified because they are too faint to be detected in broad-band images. We discuss observational properties of these strong emission-line sources. In particular, our data allow us to estimate the star formation density at z ≈ 3.7 for the first time. Subject headings: cosmology: observations — cosmology: early universe — galaxies: formation — galaxies: evolution