Photometry and the Metallicity Distribution of the Outer Halo of M31

We have conducted a wide-field CCD-mosaic study of the resolved red giant branch stars of M31, in a field located 20 kpc from the nucleus along the southeast minor axis. In our (I, V-I) color-magnitude diagram, red giant branch (RGB) stars in the top three magnitudes of the M31 halo are strongly present. We use photometry of a more distant control field to subtract field contamination and then to derive the "cleaned" luminosity function and …