Maps of optical depth τ: Herschel τ₂₅₀ (resolution 40), NICER (resolution 60), and optical depth in J band, , based on J, H, and K surface brightness maps (resolution ~2.2). In the NICER map (middle frame) the densest areas where are marked with a blue contour. The white rectangle marks the reference area used for background subtraction in the analysis. The profile cross-sections shown in Fig. 12 are taken as a median from the area between the two red lines.