L_IR/corrected Hα luminosity ratio as a function of the total extinction, A_v. The dashed lines represent the expected ratio derived from our models for various log  SFR_{1 − 10 Myr}/SFR_{10 − 100 Myr} values (red = 2, orange = 1, turquoise = 0, blue = –1, and purple = –2). The dot-dashed black line is the ratio calculated from empirical relation L_corr(Hα) = L_obs(Hα) + 0.0024 L_IR derived by Kennicutt et al. (2009) for a sample of nearby galaxies, and the dotted black lines are the uncertainty of that calibration. The contribution of the AGN torus to the IR luminosity has been subtracted when present. The color of the symbols is as in Fig. 4.