  We have carried out a wide-field imaging survey for [OII]3727 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 (Delta_z = 0.03),
corresponding to a survey volume of 5.56*10^5 Mpc^3. We obtain a sample of 3176
[OII] emitting galaxies with observed emission-line equivalent widths greater
than 26 AA. Since our survey tends to sample brighter [OII]3727 emitting
galaxies, we also analyze a sample of fainter [OII]3727 emitting galaxies found
in the Subaru Deep Field (SDF). We find an extinction-corrected [OII]
luminosity density of 10^{40.35^+0.08_-0.06} ergs s^-1 Mpc-3, corresponding to
star formation rate density of 0.32^+0.06_-0.04 M_sun yr-1 Mpc^-3 in the COSMOS
field at z~1.2. This is the largest survey for [OII]3727 emitters beyond z=1
currently available.
