Power-law indices of the temperature dependence of the CO (top) and H₂ (bottom) non-LTE cooling functions (solid line; see Sect. 6.2). The fits are valid for a temperature range between 30 and 150 K for CO and 150 and 1000 K for H₂. The fitted β values form the models with n_H2 = 10^4.5 cm^-3 and n_H2 = 10⁶ cm^-3 are also plotted for each galaxy. For visualization the abscissa of the data points are slightly offset.