The [O II] λ3727 luminosity function at z 1

We measure the evolution of the [O II] λ3727 luminosity function (LF) at 0.75 < z < 1.45 using high-resolution spectroscopy of 14,000 galaxies observed by the Deep Extragalactic Evolutionary Probe 2 galaxy redshift survey. We find that brighter than the LF is well represented by a power law dN/dL L ^α with slope α -3. The number density of [O II]-emitting galaxies above this luminosity declines by a factor of ≳2.5 between z ∼ 1.35 and z ∼ 0.84. In the limit of no number-density evolution, the characteristic [O II] luminosity, , defined as the luminosity where the space density equals 10^-3.5 dex^-1 Mpc ^-3, declines by a factor of 1.8 over the same redshift interval. Assuming that is proportional to the star formation rate (SFR), and negligible change in the typical dust attenuation in galaxies at fixed [O II] luminosity, the measured decline in implies a ∼ 25% per Gyr decrease in the amount of star formation in galaxies during this epoch. Adopting a faint-end power-law slope of -1.3 ± 0.2, we derive the comoving SFR density in four redshift bins centered around z 1 by integrating the observed [O II] LF using a local, empirical calibration between and SFR, which statistically accounts for variations in dust attenuation and metallicity among galaxies. We find that our estimate of the SFR density at z ∼ 1 is consistent with previous measurements based on a variety of independent SFR indicators.