Comparisons of the observational constraints on EW₀ with the models of Schaerer (2003), Raiter et al. (2010). These models show evolution of the spectral properties of stellar populations for stellar ages varying from 10⁴ yr to 1 Gyr for the starburst SFH (left panel) and the constant SFH (right panel). Different colors correspond to six metallicities: Z = 0 (PopIII, blue), 5 × 10^-6Z_⊙ (cyan), 5 × 10^-4Z_⊙ (green), 0.02 Z_⊙ (yellow), 0.2 Z_⊙ (magenta), and Z_⊙ (red). For each metallicity, the colored shaded regions denote EW₀ ranges traced by the three three power-law IMFs: two Salpeter IMFs (1−100 M_⊙ and 1−500 M_⊙) and a Scalo IMF (1−100 M_⊙). The horizontal gray shaded regions indicate the range of nine very large EW₀ LAEs without signatures of mergers or AGNs.