Background-subtracted surface density profiles of the Eastern (blue open circles) and Western (red filled circles) wings of the density distribution shown in Fig. 11, from counts of RGB stars selected with the same box used for the density maps (see Fig. 12). Upper panel: profiles along the Y direction. Lower panel: profiles along the  |X|  direction; the adoption of the absolute value of X allows to compare the Eastern to the Western wing in the same scale. The dashed line is the best linear fit to the distribution of points from both wings. In all the cases only stars within  |Y|  ≤ 1.5′ and 4′ ≤  |X|  ≤ 8′ have been considered.