Comparison of the line cooling with the infrared continuum cooling. The background colors show the total infrared flux integrated from wavelengths starting at 11 μm (Koumpia et al. 2015). The contours give the decadic logarithm of the ratio of the integrated line flux relative to the continuum flux. In the top panel we use the sum of the [O i] and [C ii] fluxes, in the lower panel, we only show the [C ii]/TIR ratio as used in many existing investigations.