Left: foreground-corrected dust column-density map (as shown in Fig. 1) in greyscale. The black contour indicates the A_v = 15 level. The red contours show the same A_v = 15 level from the H₂ column-density map derived from N₂H⁺, using an excitation temperature of 10 K and an abundance of 2 × 10^-9. Right: dust temperature map of Cygnus X North from Herschel with the same red A_v = 15 contour from N₂H⁺.