The predicted star formation rate as function of galactic age for the model galaxies. Note that the setup for the dust and adopted yields do not modify the predicted star formation rate. Therefore each line in the plot is representative of all models with a given mass. The horizontal lines correspond to a SFR = 40   M_⊙   yr^-1, which is the estimated value for MS 1512-cB58(Pettini et al. 2002), and to SFR = 3 × 10³   M_⊙   yr^-1, which is the value inferred for J1148+5251, respectively.