Radial excess profiles. Shown are exposure-corrected excess counts per unit sky area. Upper panel: profiles for different energy bands. Lower panel: profiles for different segments as defined in Fig. 1b. The black curve, showing the total excess above threshold in all segments, is the same in both panels. All profiles are normalised to equal area, to allow an easy comparison. The profiles have been computed with respect to a centre point at RA 16^h46^m36^s, Dec −46° 01′12″, slightly shifted from the Westerlund 1 position. In the calculation of the profiles, we discarded pixels within 0.6° of the position of HESS J1640−465.