Left: CFHT/MEGACAM i-band images of our galaxies, unless stated otherwise, in a 6″  ×  6″ snapshot, centred on the galaxies coordinates. Middle: ALMA map of the CO(3-2) emission around our galaxies. Spatial scale is the same as in the left panel. The colour wedge of the intensity map is in mJy beam⁻¹ km s⁻¹. The contours are defined such that they are spaced by 2 times the rms starting at 1 time above the rms. In the bottom right corner is the beam size. Right: the spectrum shows the flux, S_CO, spatially integrated as indicated in Sect. 2.2, of the source in mJy in function of the velocity in km s⁻¹, with respect to a fixed frequency. The Gaussian profiles are fits of the emission lines from which we derived our FWHMs. The yellow filled zones correspond to the spectral extent of the emissions. The green vertical line corresponds to the spectroscopic redshift.