Relationship between T[N II] and T[S III] (top), T[O III] and T[N II] (middle), and T[O III] and T[S III] (bottom) measured for H II regions in NGC 5457. The empirical relations from CHAOS observations as drawn as a solid black line while the photoionization models of Garnett (1992) are drawn as a dashed blue line. These temperature–temperature relations are characterized by intrinsic dispersions of 290 ± 60 K, 280 ± 140 K, and 1050 ± 160 K.