Optical three-colour composite of each group galaxy in our sample with overlaid H I contours. The colour image is comprised of the g-, r-, and i-band filters from the FDS (Iodice et al. 2016); the white dashed contour shows the most sensitive, constant column density of N_H I = 1.4 × 10¹⁹ atoms cm⁻² from Fig. 2 and the blue contours start from the local column density sensitivity (i.e. 1.4 × 10¹⁹ atoms cm⁻² scaled by the primary beam response; see top left corner of each cutout) and increase by a factor of 3ⁿ with n = 0, 1, 2, ..., at each step. For non-detections, the 3σ H I column density upper limit over a single channel is shown in red in the top left of the cutout. The restoring beam (33.0″ × 29.2″) is shown in orange in the bottom left corner and a 5 kpc scale bar is shown in the bottom right corner.