Color-composite images of NGC 6860, Mrk 915, and MCG -01-24-012, generated with g − r − i − z filters from the archival Dark Energy Camera images. North is up and east is left, as in all other figures in the paper. The rectangles correspond to the FoV of the maps in Fig. 2. The central gray rectangle in the left image masks an artifact present in the i- and z-band images of NGC 6860. In Appendix A, we describe how these figures were generated.