Emission-Line Galaxies in the STIS Parallel Survey. II. Star Formation Density

We present the luminosity function of [O II]-emitting galaxies at a median redshift of z = 0.9, as measured in the deep spectroscopic data in the STIS Parallel Survey (SPS). The luminosity function shows strong evolution from the local value, as expected. By using random lines of sight, the SPS measurement complements previous deep single-field studies. We calculate the density of inferred star formation at this redshift by converting from [O II] to Hα line flux as a function of absolute magnitude and find = 0.043 ± 0.014 M☉ yr-1 Mpc-3 at a median redshift z ~ 0.9 within the range 0.46 < z < 1.415 (H0 = 70 km s-1 Mpc-1, ΩM = 0.3, ΩΛ = 0.7). This density is consistent with a (1 + z)4 evolution in global star formation since z ~ 1. To reconcile the density with similar measurements made by surveys targeting Hα may require substantial extinction correction.