CMD in different radial annuli, from the centre of the bulge to the edge of the ACS image. For R ≳ 50.0″ we split the annuli in their northern and southern halves (NH and SH, respectively) in order to highlight the asymmetry in the surface density related to the SW over-density. In the corresponding panels, we also report the ratio between AGB and RGB stars. The horizontal grey line marks the position of the RGB tip as determined from the whole sample. This series of CMDs also clearly illustrate the severe effect of the increasing incompleteness towards the centre of the most crowded substructure, i.e. the bulge, with the limiting magnitude dropping by nearly 2 mag from R >  30.0″ to R <  10.0″.