MOSEL: Strong [OIII] 5007 angstrom Emitting Galaxies at (3 < z < 4) from the ZFOURGE Survey

To understand how strong emission-line galaxies (SELGs) contribute to the overall growth of galaxies and star formation history of the universe, we target SELGs from theZFOURGEimaging survey that have blended H beta+[OIII] rest-frame equivalent widths of >230 angstrom and 2.5 < z(phot) < 4.0. Using Keck/MOSFIRE, we measure 49 redshifts for galaxies brighter than K-s = 25 mag as part of our Multi-Object Spectroscopic Emission Line (MOSEL) survey. Our spectroscopic success rate is similar to 53% and sigma z = [Delta z/(1+z)] = 0.0135. We confirm 31 ELGs at 3 < z(spec) < 3.8, and show that SELGs have spectroscopic rest-frame [OIII]5007 angstrom equivalent widths of 100-500 angstrom and tend to be lower-mass systems [log(M-star M-circle dot) similar to 8.2-9.6] compared with more typical starforming galaxies. The SELGs lie similar to 0.9.dex above the star-forming main sequence at z similar to 3.5 and have high inferred gas fractions of f(gas) greater than or similar to 60%, i.e., the inferred gas masses can easily fuel a starburst to double stellar masses within similar to 10-100 Myr. Combined with recent results using ZFOURGE, our analysis indicates that (1) strong [O III] 5007 angstrom emission signals an early episode of intense stellar growth in low-mass [M-star < 0.1 M-star] galaxies and (2) many, if not most, galaxies at z > 3 go through this starburst phase. If true, low-mass galaxies with strong [O III] 5007 angstrom emission (EWrest > 200 angstrom) may be an increasingly important source of ionizing UV radiation at z > 3.