Relation between the ionized gas mass and size (M_H II − R_H II) and between the stellar mass and size (M_∗ − R_H II) for H II regions, color-coded by their SFR surface densities. The solid black lines represent the best-fit relations for M_H II − R_H II and M_∗ − R_H II. The solid colored lines indicate three different feedback mechanisms from Krumholz et al. (2019): supernovae (SNe), direct radiation pressure (DR), and photoionization feedback (ionization), with their corresponding slopes (a = 3, a = 2, and a = 1). The other markers are the same as in Fig. 7.