[O III] emission line as a tracer of star-forming galaxies at high redshifts: comparison between Hα and [O III] emitters at z=2.23 in HiZELS

We investigate the properties of z = 2.23 H alpha and [O III] lambda 5007 emitters using the narrow-band-selected samples obtained from the High-z Emission Line Survey. We construct two samples of the H alpha and [O III] emitters and compare their integrated physical properties. We find that the distribution of stellar masses, dust extinction, star formation rates (SFRs), and specific SFRs (sSFRs) is not statistically different between the two samples. When we separate the full galaxy sample into three subsamples according to the detections of the H alpha and/or [O III] emission lines, most of the sources detected with both Ha and [O III] show log(sSFR(UV)) greater than or similar to -9.5. The comparison of the three subsamples suggests that sources with strong [O III] line emission tend to have the highest star-forming activity out all galaxies that we study. We argue that the [O III] emission line can be used as a tracer of star-forming galaxies at high redshift, and that it is especially useful to investigate star-forming galaxies at z > 3, for which Ha emission is no longer observable from the ground.