The [O II] lambda 3727 Luminosity Function at z ~ 1

TL;DR

This study measures the evolution of the [OII] luminosity function at z~1, revealing a decline in star formation activity and galaxy luminosity over this epoch, consistent with previous SFR estimates.

Contribution

It provides the first detailed measurement of the [OII] luminosity function evolution at 0.75<z<1.45 using high-resolution spectroscopy of ~14,000 galaxies.

Findings

The [OII] luminosity function follows a power law with slope ~ -3 for L_{OII}>10^{42} erg s^{-1}.

The characteristic [OII] luminosity declines by a factor of ~1.8 from z~1.35 to z~0.84.

The star formation rate density at z~1 is consistent with previous measurements.

Abstract

We measure the evolution of the [OII]lambda 3727 luminosity function at 0.75<z<1.45 using high-resolution spectroscopy of ~14,000 galaxies observed by the DEEP2 galaxy redshift survey. We find that brighter than L_{OII}=10^{42} erg s^(-1) the luminosity function is well-represented by a power law dN/dL ~ L^{\alpha} with slope \alpha ~ -3. The number density of [OII] 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 [OII] luminosity, L^*_[OII], 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 L_[OII] is proportional to the star-formation rate (SFR), and negligible change in the typical dust attenuation in galaxies at fixed [OII] luminosity, the measured decline in L^*_[OII] 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\pm0.2, we derive the comoving SFR density in four redshift bins centered around z~1 by integrating the observed [OII] luminosity function using a local, empirical calibration between L_[OII] 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.