Residual [C II] 158 μm spectrum (dashed line and gray filled histogram) at offset position (–30′′, –15′′), after subtracting, from the original [C II] spectrum, the scaled up (*) spectra of model 1-(top), 2-(middle) and 3-(bottom), as well as the optical depth of H I, τ(H I) (see text). All negative (noise) channels in the scaled up and residual spectra are set to zero. The residual [C II] spectrum is shifted in −1 K for clarity.