Nonthermal fraction at 5 GHz of radio sources associated with MIR sources in exposed HII regions shown in (a1) for small sources, in (b1) for medium sources, and in (c1) for large sources as a function of the radio flux density at the same frequency. Filled triangles are the median values and open circles are the mean values with the standard deviations. Colors indicate different apertures: green for R_ap = R_s, blue for R_ap = 1.5R_s and magenta for R_ap = 2R_s. Left panels: number of sources in each bin for sources of small (top), medium (middle), and large (bottom) size. Right panels: nonthermal fractions for R_ap = R_s (open green circles), in the annulus between R_s and 1.5R_s (open blue squares) and between 1.5R_s and 2R_s (open magenta squares) for small, medium, and large sources (a2, b2, c2 respectively). Radio flux units are mJy.