Left panels: nonthermal-to-total-radio-continuum flux density ratio at 5 GHz for radio sources associated to exposed YSCs (blue circles) using apertures with R_ap = 1.5R_s for small (a1), medium (b1), and large (c1) sources. In the same panels we show the nonthermal-to-total-radio flux density ratio for the GMCs hosting the YSCs (red squares) as a function of the radio emission of the YSCs. We underline that not all YSCs considered here have an associated GMC. Right panels: total-to-thermal radio flux ratio for the whole ensemble of GMCs hosting exposed YSCs (filled symbols), binned according to their star formation rate per unit area. Radio continuum has been used to estimate the SFR density (red squares). From top to bottom we compare the ratios relative to GMCs with the ratios relative to small, medium, and large sources respectively (open blue circles) binned according to the SFR per unit area. The area around the source is circular with a radius of 1.5R_s.