(a) Mass-corrected self-absorption vs. 70 μm flux, and (b) the ratio , equivalent tothe dissociation rate of the C¹⁸O, vs. the flux ratio F_70μm∕F_250μm of the distinct regions. Selected regions are marked with the letters A to I. The average fluxes of the infrared 70 and 250 μm images of the distinct regions in both panels were obtained from the data of the Herschel Gould Belt Survey Archive.