Stamps showing the surface brightness radial profile of each galaxy in our sample. The galaxy ID number is shown at the bottom left corner of each stamp. The colour-code is the same as in the main text, i.e. the horizontal pink dashed-line shows the 1σ standard deviation level of the map, the beige solid line shows the radial profile of the synthesised beam and the purple solid line shows the radial profile of the CO(2–1) emission.