Metallicity distribution for the halo stars in NGC 5128 and M 87. The upper two panels show the MDF (number of stars per 0.1-dex metallicity interval) from three locations in the halo of NGC 5128 (see text). In the bottom panel, the shaded histogram shows the MDF for the stars in the M 87 inner halo in the magnitude range I = 27.0−28.0, uncorrected for photometric completeness or color bias. The heavy red solid line shows the MDF now fully corrected for those effects, while the heavy green dashed line shows the metallicity range in which the deduced MDF is most reliable. This corrected MDF for M 87 is repeated in the middle panel (dashed line) for direct comparison with the inner-halo field in NGC 5128 (vertical scaling is arbitrary for display purposes).