Mid-infrared extinction as a function of distance in the direction of the remnant. The points and uncertainties correspond to mean and standard deviation of values reported by Schultheis et al. (2014) averaged within a circle with radius of 0.25° centred on the CCO. The red line shows the extinction as a function of distance for the dense filament marked in Fig. 11 (the respective uncertainties are not shown for clarity, but they are a factor of two smaller than for the black points).