Comparison of the gas-to-dust ratio with the ratio between CO( J=2-1) and IRAS 60 μm and R_FUV/NUV (left and right respectively). The colour and shape of the markers represent the stellar variability and chemistry type as in Fig. 4. Empty triangles are upper limits for the CO( J=2-1) intensities. Grey markers represent NESS sources. The values of R_FUV/NUV shown in this figure were not corrected from dust attenuation. It can be appreciated a correlation and an anticorrelation in the figures on the left and right respectively.