Line profiles of the H110α line for two cases. The result in the case of ultra-compact HII region + EE is presented in the top panel, and that of hyper-compact H II region + EE is shown in the bottom panel. The values of n_e are 10⁶, 10⁵, and 10² cm⁻³ for the hyper-compact, ultracompact, and extended H II regions, respectively, and the corresponding EMs are 10⁸, 5 × 10⁷, and 10⁵ cm⁻⁶ pc. The electron temperature is T_e = 10 000 K.