We have used Suprime-Cam on the Subaru Telescope to conduct a V - and I -band imaging survey of fields sampling the spheroid of the Andromeda galaxy along its south-east minor axis .
Our photometric data are deep enough to resolve stars down to the red clump .
Based on a large and reliable sample of red giant stars available from this deep wide-field imager , we have derived metallicity distributions vs. radius and a surface brightness profile over projected distances of R = 23 –66 kpc from the galaxy ’ s center .
The metallicity distributions across this region shows a clear high mean metallicity and a broad distribution ( [ Fe/H ] \sim - 0.6 \pm 0.5 ) , and indicates no metallicity gradient within our observed range .
The surface brightness profile at R > 40 kpc is found to be flatter than previously thought .
It is conceivable that this part of the halo samples as yet unidentified , metal-rich substructure .