RADEX best-fit model compared to observations for the CO excitation ladder of NGC 1140; the observations have been corrected for beam size as described in Sect. 4, and normalized to the CO(1–0) flux. The observations are shown as filled blue circles (¹²CO) and red squares (¹³CO), and the range of the allowed RADEX models by the light-blue region (for ¹²CO); ¹³CO points have arbitrarily offset relative to ¹²CO for clarity. The dashed curve shows the ν² behavior (here normalized to J = 1) expected for optically-thick emission.