Left:¹²CO(8–7) emission map showing a FoV of 3 × 3 spaxels (35″ each; light green square) considered when combining the SSW and SLW SPIRE data at the same resolution (i.e., 35″, large spatial scale). The peak emission (in red) and a ring of one spaxel width around that maximum (green area) are identified. Middle: excitation temperatures (T_ex) and the (logarithmic) column densities (N_CO) are derived for each spaxel using the rotational diagrams. The yellow boxes represent the spectra characterized by high T_ex and N_CO values. Right:¹²CO/IR flux ratios computed for the different J transitions in the SPIRE domain. In red are shown the values derived at the position of the flux density peak (spaxel #5 in the left panel) while in green the ratios derived integrating the emission in the ring. The ratio between the maximum peak and the ring for each transition is also shown (i.e., “peak-to-ring ratio”, in blue) divided by 100 (a factor of 100 has to be applied to obtain the real values). The dashed gray lines identify the lower and upper limit values of the peak-to-ring ratios computed within the errors. Higher ¹²CO/IR values are derived for high J (J_up ≥ 11–10) in the ring structure, implying lower (≲1) peak-to-ring ratios.