Surface brightness profiles of the gas distribution of the galaxies BRI1335−0417, J081740 and the SGP38326 system, respectively from top to bottom. Left panels: surface brightness map of the [CII] emission. The emission is shown as contours in turquoise for the data and magenta for the model. The contour levels follow levels of emission of 4σ, 8σ and 16σ, where σ is the RMS noise in the total map. We show the beam of the observations in the bottom left. Middle panel: residual map normalised by the RMS noise according to the colourbar shown. We show the centre of the best-fit model of each galaxy with a small cross. Right panel: 1D profile of the average gas emission in concentric ellipses (turquoise) and the best-fit Sérsic model (magenta), the dotted line shows the 4σ level above the noise. In the bottom panel we show the galaxies SGP38326−1 and SGP38326−2 together, as they have to be fitted simultaneously, and we mask the emission of SGP38326−3 in the bottom left corner.