Flux maps of the HESS J1646−458 region. The position of Westerlund 1 is marked by the black star symbol; the grey, dashed line shows the Galactic plane. Coloured symbols indicate objects listed in the legend in panel a. Dark grey square markers denote positions of sources from the 4FGL-DR2 catalogue (Abdollahi et al. 2020; Ballet et al. 2020), where those sources that are still significant () above 30 GeV are shown with a diamond marker (◇). Grey circles labelled ‘A’ and ‘B’ mark regions defined in Abramowski et al. (2012); region ‘C’ (at RA 16^h49^m4.8^s, Dec −46° 06′00″) is newly defined here. The white circle marker indicates the coordinate with respect to which the radial profiles in Figs. 4 and 9a have been computed. The scale bar denotes a projected distance of 40 pc, for the nominal distance to Westerlund 1 of 3.9 kpc. The maps are for different energy thresholds, indicated at the bottom of each panel. The maps in panels a, c, and d were computed using a 0.22° top-hat smoothing kernel, while the map in panel b was computed using a 0.07° Gaussian smoothing kernel. Colour scales are saturated at the maximum observed flux value associated with the HESS J1646−458 region. Contour lines shown in blue are at flux levels of F = (12.5/20/27.5)×10⁻⁹ cm⁻² s⁻¹ sr⁻¹ for panels a and b, at F = (3/5.5/8)×10⁻⁹ cm⁻² s⁻¹ sr⁻¹ for panel c, and at F = (1/1.5)×10⁻⁹ cm⁻² s⁻¹ sr⁻¹ for panel d.