Predicted [O i] 63 and 145 μm and [C ii] 157 μm fine-structure fluxes as a function of the gas temperature. The fourth panel shows the predicted ratio between the [O i] 63 and 145 μm fluxes. The observed ratio is overplotted by the horizontal dashed lines. The total disk gas masses in M_⊙ are indicated. The blue box encompasses gas temperatures between 30 and 70 K and the observed [O i] at 63 μm, [O i] at 145 μm, [C ii] at 157 μm, and the F([O i]145 μm)/F([O i]63 μm) flux with 3σ error bars.