Top panel: best-fitting model for the SED of NGC 23 (constant SFH, see Sect. 5.1) in a solid black line, together with the observed data (red diamonds). The Hα luminosity and model prediction in L_⊙ units are plotted at λ = 6563 Å (red diamond and solid black circle, respectively) multiplied by a factor of 10³. The solid color lines indicate the contribution of the different stellar populations with ages <10 Myr (blue), 10−100 Myr (dark green), 100–500 Myr (light green), 0.5–1.5 Gyr (orange), and > 1.5 Gyr (pink). The blue and red dashed lines are the dust emission for dust temperatures lower and higher than 50 K, respectively. The dotted green line is the AGN torus model derived by Alonso-Herrero et al. (2012a). The residuals are shown in the lower part of the panel. Bottom panels: likelihood distribution for several of the physical parameters (IR dust luminosity, SFR, stellar mass, ISM extinction μτ_v, young stars extinction τ_v, ratio between the ISM and young stars extinctions μ, fraction of IR luminosity produced by cold dust with T< 50 K removing the AGN contribution f_μ, fraction of IR luminosity due to PAH emission, and dust mass). The next five panels show the logarithm of the percentage of the stellar mass for different stellar age ranges using the same color coding as in the top panel. The last panel represents the SFH.