Example of the peak flux as a function of the in-band frequency for bright sources (top panel) and faint sources (bottom panel). Each data point (circle or triangle) refers to the peak intensity at each sub-band, with the error of the peak measurement. The solid and dashed lines in the top panel show the best fit to the peak flux densities from 9 sub-bands for two bright sources: G020.0808−00.1354 (α = 1.1 ± 0.07) and G021.7700+00.8423 (α = −0.92 ± 0.04), respectively. The solid and dashed lines in the bottom panel present the spectral fitting of 5 and 6 sub-bands for two faint sources: GOll.9357+00.2871 (α = −1.7 ± 0.36) and G036.8880+01.0288 (α = 2.5 ± 0.6), respectively.