Broad-band (Rc − z′) versus (i′ − z′) colours of the three samples from the two fields of this study: z ∼ 5.7 LBGs (blue triangle), z ∼ 6 i′-dropouts (red squares) and z ∼ 5.7 LAEs (black dots). Open circles indicate LAEs in the spectroscopic sample, which is presented in a forthcoming paper. They all show a single emission line. The arrow indicates the object that is selected by both the z ∼ 5.7 LBG and the LAE criteria. The red dashed vertical line shows the (i′ − z′) = 1.3 boundary for i′-dropouts, the blue solid lines indicate the colour criteria for z ∼ 5.7 LBGs and the green dot–dashed line shows a typical boundary adopted for z ∼ 5 LBGs. The contours correspond to the full catalogue of detections in the z′ band and contain 50, 90 and 97 per cent of the sources in the catalogue.
