[OIII] emission line as a tracer of star-forming galaxies at high
  redshifts: Comparison between H$\alpha$ and [OIII] emitters at $z$=2.23 in
  HiZELS
  We investigate the properties of $z$=2.23 H$\alpha$ and [OIII]$\lambda$5007
emitters using the narrow-band-selected samples obtained from the High-$z$
Emission Line Survey (HiZELS: Sobral et al. 2013). We construct two samples of
the H$\alpha$ and [OIII] emitters and compare their integrated physical
properties. We find that the distribution of stellar masses, dust extinction,
star formation rates (SFRs), and specific SFRs, 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 [OIII] emission
lines, most of the sources detected with both H$\alpha$ and [OIII] show ${\rm
log(sSFR_{UV})}$$\gtrsim$-9.5. The comparison of the three subsamples suggests
that sources with strong [OIII] line emission tend to have the highest
star-forming activity out all galaxies that we study. We argue that the [OIII]
emission line can be used as a tracer of star-forming galaxies at high
redshift, and that it is especially useful to investigate star-forming galaxies
at $z$$>$3, for which H$\alpha$ emission is no longer observable from the
ground.
