Top: the large-scale neutral hydrogen emission (red) superimposed on a deep optical image of the galaxy from observations by Mundell et al. (1995). The figure shows the large scale (20 arcmin) of the H i plumes, suggesting that the members of Arp 94 have interacted tidally in the past. Bottom: composite g+r MegaCam/CFHT image of the Arp94 system (Duc et al. 2014) rendered with an “arcsinh stretch” to bring out the faint structure. The image, matched in scale to the H i image, shows evidence of considerable tidal debris, including shells and ripples. The southern H i plume appears to have a faint stellar counterpart whereas the northern filament is less correlated with the faint optical light.
(Appleton et al., 2014)