The ratio between the accumulated stellar initial mass of all the stars ever formed (according to the assumed SFH) and the initial gas mass of the simulation. This value can be larger than one since the stars return their mass into the gas phase when they die. The returned gas can then be recycled to form new stars. We note that the parameter f_st is different to the parameter f_trans defined in Thomas et al. (1999). The latter is not an accumulated value and cannot be larger than one.

Models with t_sf <  25 Myr and SFR >  10⁴ M_⊙ yr⁻¹ are also computed in order to cover the lower right corner of likelihood map in Figs. 3, 5, and 7 below.