Radio continuum spectra of the sample galaxies. Except for II Zw 40 (see text for the procedure and plotted lines here), the plots show the following: measured flux densities (blue squares), best fit of the radio continuum spectrum (solid red line). The best parameters are listed in the lower left part of the figure along with the reduced chi-square (). The free-free (thermal) and synchrotron (nonthermal) components of the models are depicted by the dotted cyan line and dashed green line, respectively. The green crosses represent the observed nonthermal component (i.e. the modelled thermal component removed from the observational data). The cyan stars delineate the observed thermal component (i.e. the modelled nonthermal component subtracted from the observational data). The vertical yellow dash-dotted line marks the break frequency ν_b . (Continuation of Fig. 1).