Maps of the ratio between images obtained at the g- and z-bands (from Dark Energy Camera), used as a proxy for dust attenuation. The CO(2-1) M₀ outer contours are overlaid in blueish-green color. The near side of the disk is the southeast and the northwest in NGC 6860, and MCG -01-012-24, respectively. For Mrk 915, the g / z map (middle panel) suggests that the near side of the disk could be in the east, but this would result in Mrk 915 having a rare case of leading arms (see discussion in Sect. C).