Left: CC derived from the processing of the Ko observation shown in Fig. 3 (red), measured CC for the QS (orange) with 1σ uncertainty (black) and the whole background (blue). The slope of the derived CC is also shown. Right: distribution of density values for the QS (blue), AR (red) and whole disc (black). The horizontal dashed line in both panels denotes the highest value of the QS CLV.