SED of two pixels (top: non-molecular region, bottom: molecular region). The squares are data, the solid line is the fitted model, and the crosses are the fitted model integrated within the bands. The fits are performed using the 100  μm, 857, 545, 353 and 143 GHz bands (red squares), and using the statistical noise discussed in Sect. 2, which is too low to be visible on the figure. Significant excess in the 217 and 100 GHz bands caused by ¹²CO and ¹³CO emissions are detected in the molecular spectrum. The 60  μm data points are not used to analyse the SEDbecause of the contribution of small dust particles transiently heated each time they absorb a UV/visible photon.