The distribution on the sky of the cluster galaxies (as determined by COMBO-17; denoted cmc17 in the legend) in the F21 and F22 regions down to m_R < 23. ELGs (where H α has been securely detected) are represented by green filled circles. Galaxies classified as AGN or star forming with ≥3σ confidence are shown as solid red circles and blue stars, respectively. The centres of A901a and A902 (determined from the brightest cluster galaxies) are marked with black crosses. The large dashed circles show the r₂₀₀ radii of A901 and A902 derived from the weak lensing analysis of Heymans et al. (2008).