A selection of H{\alpha} emitters at z = 2.1-2.5 using the Ks-band photometry of ZFOURGE

Large and less-biased samples of star-forming galaxies are essential to investigate galaxy evolution. H\(\rm\alpha\) emission line is one of the most reliable tracers of star-forming galaxies because its strength is directly related to recent star formation. However, it is observationally expensive to construct large samples of H\(\rm\alpha\) emitters by spectroscopic or narrow-band imaging survey at high-redshifts. In this work, we demonstrate a method to extract H\(\rm\alpha\) fluxes of galaxies at \(z=2.1\)-\(2.5\) from \(K_s\) broad-band photometry of ZFOURGE catalog. Combined with 25-39 other filters, we estimate the emission line fluxes by SED fitting with stellar population models that incorporate emission-line strengths. 2005 galaxies are selected as H\(\rm\alpha\) emitters by our method and their fluxes show good agreement with previous measurements in the literature. On the other hand, there are more H\(\rm\alpha\) luminous galaxies than previously reported. The discrepancy can be explained by extended H\(\rm\alpha\) profiles of massive galaxies and a luminosity dependence of dust attenuation, which are not taken into account in the previous work. We also find that there are a large number of low-mass galaxies with much higher specific star formation rate (sSFR) than expected from the extrapolated star formation main sequence. Such low-mass galaxies exhibit larger ratios between H\(\rm\alpha\) and UV fluxes compared to more massive high sSFR galaxies. This result implies that a ``starburst'' mode may differ among galaxies: low-mass galaxies appear to assemble their stellar mass via short-duration bursts while more massive galaxies tend to experience longer-duration (\(>10\ \mathrm{Myr}\)) bursts.