Upper panel: sMdust against sSFR for LBGs (black triangles) and DGS galaxies (red dots). Different chemical evolutionary models computed with a Chabrier IMF or with a top-heavy IMF (α = 1.35) and different condensation fractions as indicated in the legend. For all the models shown we select a value of τ = 300 Myr in Eq. (1) and M_swept = 1000 M_⊙ in Eq. (8) and M_gas = 100 × M_stars. Lower panel: same as in the upper panel but overplotting models with a top-heavy IMF and different condensation fractions indicated in the legend.