We present the luminosity function of [ OII ] -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 [ OII ] to H \alpha line flux as a function of absolute magnitude and find \dot { \rho } = 0.043 \pm 0.014 M _ { \odot } yr ^ { -1 } Mpc ^ { -3 } at a median redshift z \sim 0.9 within the range 0.46 < z < 1.415 ( H _ { 0 } = 70 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { M } = 0.3 , \Omega _ { \Lambda } = 0.7 ) .
This density is consistent with a ( 1 + z ) ^ { 4 } evolution in global star formation since z \sim 1 .
To reconcile the density with similar measurements made by surveys targeting H \alpha may require substantial extinction correction .