Correlation of the absorption column measured from the spatially resolved spectral analysis of XMM-Newton data and the relative reddening derived from VVV photometry (left panel). The outlier point corresponds to region 2 where the optical extinction is underestimated due to the lack of stars in the optical data. We find N_H ~ 1 + A_V,rel/ 4 from a linear fit including a 10% systematic uncertainty for the column measured in X-rays. A composite image of the calibrated absorption column density map derived from optical extinction (red) and ATLASGAL 0.87 mm (green) maps is shown together with the X-ray 0.4–10 keV image (blue) for reference in the middle panel. We note the enhanced absorption along the western rim of the remnant, particularly along its north-western part. The same features can be traced in the composite image showing X-ray (blue), radio (green), and 350 μm Herschel/SPIRE data (right panel). The white contours correspond to Herschel data to highlight the extension of the filament in the north-west in northern direction where it bridges with the X-ray filament as shown with the northernmost yellow circle (see also the middle panel where the X-ray filament is more clearly seen). The other two circles emphasise the correspondence between the infrared and radio data along the filament.