2021ApJ...920...78B

Upcoming missions such as Euclid and the Nancy Grace Roman Space Telescope (Roman) will use emission-line-selected galaxies to address a variety of questions in cosmology and galaxy evolution in the z > 1 universe. The optimal observing strategy for these programs relies on knowing the number of galaxies that will be found and the bias of the galaxy population. Here we measure the [O III] λ5007 luminosity function for a vetted sample of 1951 m_J+JH+H < 26 galaxies with unambiguous redshifts between 1.90 < z < 2.35, which were selected using Hubble Space Telescope (HST)/WFC3 G141 grism frames made available by the 3D-HST program. These systems are directly analogous to the galaxies that will be identified by the Euclid and Roman missions, which will utilize grism spectroscopy to find [O III] λ5007-emitting galaxies at 0.8 <= z <= 2.7 and 1.7 <= z <= 2.8, respectively. We interpret our results in the context of the expected number counts for these upcoming missions. Finally, we combine our dust-corrected [O III] luminosities with rest-frame ultraviolet star formation rates to present a new calibration of the star formation rate density associated with 1.90 < z < 2.35 [O III]-emitting galaxies. We find that these grism-selected galaxies contain roughly half of the total star formation activity at z ∼ 2.