Nonlocal and NLTE [O I] excitation and radiative transfer models: Predicted [O I] 145 µm line intensity (left) and [O I] 63/145 µm intensity ratio in cgs units (right) as a function of total gas density. The black, grey, and blue curves represent different column densities of atomic oxygen. Dotted curves represent models with external FIR illumination (see text). In the left panels, the red and cyan dashed lines show the [O I]145 µm intensities measured toward Peak 1 in the red- and blueshifted wings, respectively. In the right panels, the red and cyan dashed colored areas show the intensity ratios (with errors) measured toward Peak 1 in the red- and blueshifted wings, respectively (see Table 1).