Equivalent single stellar population age (upper panel), metallicity (central panel) and α-enhancement (lower panel) measured in S_model. S_model represent a composite stellar population formed by stars from the halo around NGC 3311 contaminated by a fraction F of stars from dwarf galaxies (see Sect. 4.2 for details). Long-dashed green and short-dashed magenta lines represent the mean values of age, [Z/H] and [α/Fe] measured in the long-slit bins E and D, respectively. The range of F values consistent with measurements in bins E and D are shaded in green and magenta, respectively.