Semi-circular region (left panel), with the pulsar at the apex and a mask applied over LS 5039, was extracted from the excess maps to form a radial profile of the emission (right panel), shown here for the full energy range with analysis A. A mask was also applied over HESS J1826–130, which is particularly relevant for measuring the northern extent. The radial profile was fitted by a polynomial (Eq. (1)) to characterise the extent of the emission. Dashed and dotted lines mark the radial distance at which the emission drops to 1∕e and 10% of the peak value, respectively.