Redshift distribution of three typical cases. The histograms show the distribution of photometric redshifts of galaxy members. Top panel: cluster candidate located within one redshift slice; the vertical line in this panel gives the mean photometric redshift value. Middle panel: flat distribution, indicating that this overdensity is not a physically connected structure. Bottom panel: distribution of a real structure, but its peak is close to the edge of our selection redshift slice, missing a large fraction of its galaxy members.