Hα fluxes in erg cm⁻² s⁻¹ measured through aperture photometry at the location of radio sources associated with MIR emission shown in panel a as a function of the radio flux recovered from catalogd data at 5 GHz in mJy. Color coding is the same as in Fig. 1 but open symbols have been used. Right panel b: display for the same sources the Hα flux corrected for internal extinction. Filled symbols indicates radio fluxes from aperture photometry at 6.3 GHz of b- and c-type MIR sources with no catalogd radio counterpart. The predicted Hα emission if the radio flux were due to free-free radiation only is shown with a dashed line. The star symbols indicate the presence of identified SNR in the regions (catalog code > 8).