Spectral energy distribution of S43 (shown here as a representative example), based on optical/near-IR broadband photometry. The red points with error bars represent the observations of SDSS (ugriz bands), and of Spitzer/IRAC 3.6 and 4.5 μm observations. The black curve is the overplotted best-fit stellar synthesis model, obtained with the FAST code (see text). An exponential star-formation history, where time scale tau is assumed, with a Salpeter IMF. Values for tau and population age are given in yr, as well as stellar mass (M_⊙), visual extinction (mag) SFR (M_⊙/yr), or specific SFR (yr^-1). All values are in log, except A_v.