a) 870 μm continuum emission sum map of Cha III at scale 5. The contour levels are  − a (in dotted blue), a, 2a, and 4a, with a = 34.5 mJy/21.2″-beam, i.e., about 3 times the rms noise level. b) Smoothed map, i.e., residuals, at scale 5. The contour levels are  − c (in dotted blue), c, 2c, 4c, and 8c, with c = 8.1 mJy/21.2″-beam, i.e., about 3 times the rms noise level in this map. The grayscales of both maps are different. The sum of these two maps is strictly equal to the original map (Fig. 2).