The [O II] λ3727 luminosity function and star formation rate at z ≈ 1.2 in the COSMOS 2 square degree field and the Subaru deep field

We have carried out a wide-field imaging survey for [O II] λ3727 emitting galaxies at z ≈ 1.2 in the HST COSMOS 2 square degree field using the Suprime-Cam on the Subaru Telescope. The survey covers a sky area of 6700 arcmin ² in the COSMOS field, and a redshift range between 1.17 and 1.20 (Δz = 0.03), corresponding to a survey volume of 5.56 × 10 ⁵ Mpc ³. We obtain a sample of 3176 [O II] emitting galaxies with observed emission-line equivalent widths greater than 26 Å. Since our survey tends to sample brighter [O II] emitting galaxies, we also analyze a sample of fainter [O II] emitting galaxies found in the Subaru Deep Field (SDF). We find an extinction-corrected [O II] luminosity density of 10 ^{40.35-0.06+0.08} ergs s ^-1 Mpc ^-3, corresponding to star formation rate density of 0.32 _-0.04 ^+0.06 M _⊙ yr ^-1 Mpc ^-3 in the COSMOS field at z ≈ 1.2. This is the largest survey for [O II] emitters beyond z = 1 currently available.