Scatter plot of the integrated intensities of the 2_1,2–1_1,1 (E₂) CH₃OH line (blue circles) and the 3_2,2–3_1,3c-C₃H₂ line (green circles) with respect to the H₂ column density inferred from the SPIRE observations (see text). The average error bars are shown in the upper part of the plot. The average errors are 14 mK km s^-1 for CH₃OH and 4 mK km s^-1 for c-C₃H₂. Only the pixels where the integrated intensity over the average error is larger than 3 are plotted.