アブストラクト：
 It has recently been suggested that high-redshift galaxies, especially low-mass ones, may undergo episodic star formation (SF). In the theoretical works, low mass model galaxies have episodic SF histories (SFH) because of bursty SFs and subsequent outflows of ISM gas (e.g., Hopkins et al. 2014; Muratov et al. 2015). Observationally, episodic SFHs are suggested, although indirectly, from constant ages and stellar masses at a fixed luminosity over a redshift interval (e.g., Stark et al. 2009) and from short SF duty cycles inferred from clustering (e.g., Lee et al. 2009). The SED of galaxies with an episodic SF cannot be reproduced by a classically assumed SFH (SSP, const, declining, rising) but requires, to the first order, two stellar population components, one approximating past SF events by a smooth SFH and the other corresponding to the on-going SF. Indeed, such two-component galaxies have recently been found serendipitously through SED fitting to multiband photometry supplemented with emission line data( z >5 LAEs, Stark et al. 2014; Rodr ́ıguez Espinosa et al. 2014).  However, it is not known what galaxies have a two-component SED and what properties each component has, because of the few observations of such galaxies.  We have developed a method for efficiently selecting galaxies with a two-component SED based on UV multiband photometry alone, enabling a census of episodic-SF galaxies for the first time. We apply this method to our large sample of confirmed z = 2.2 Lyα emitters (LAEs) and find two promising candidates.In order to show that their entire SEDs are consistently explained by two stellar population components, spectroscopic observations of their Hα line are essential for breaking the degeneracy between stellar continuum and nebular emission in the photometric data.  In this presentation, I will introduce this new method and discuss the nature of the two candidates. I will also discuss the applications of this method with future data.