Assessment of the purity of the red-sequence samples. At redshifts above z_red > 0.4 red sequence galaxies (shown in red) and high confidence stars (shown in blue) reside in separated regions of the 2D (r − K_s)×(r − Z) colours, shown in the left panel. Shown by a pink dashed line is the predicted decision boundary between the two classes. The red sequence candidates falling below the predicted boundary are marked by open circles. These objects are flagged as likely stellar objects in the final catalogue, and thus removed from our large-scale structure analysis. Purity fraction of the dense (green dashed line) and the luminous (orange dashed line) samples as a function of redshift, in the right panel.