Galaxy images and residual cutouts around the two galaxies, ∼4 × 5 arcmin² (∼30 × 40 kpc²) on a side. North is up and east is left. Left: NGC 3640 (upper galaxy) and NGC 3641 (lower galaxy) in the u, g and r-band, from the top to the bottom, respectively. Right: galaxies-subtracted images. The observation of the u (first row) and g (second row) residuals do not show obvious dust features, contrary to previous findings (Prugniel et al. 1988).