Comparison of the free-free SEDs used as examples. Filled black circles represent data for G24.78+0.08 A1 (Cesaroni et al. 2019). The solid black line is the SED calculated with Cloudy and normalised to the data at 44 GHz. The dashed black line is the theoretical SED with T_K = 10⁴K and EM = 1.3 × 10⁹ pc cm⁻⁶. The solid blue line is the SED calculated with Cloudy for the second example. The solid red line is a theoretical SED with T_K = 10⁴ K and EM = 3.9 × 10¹⁰ pc cm⁻⁶.