Distribution of R_1/2 (in arcsec) versus CS for sources in the random sample. We present saturated sources as black diamonds, blended stars as blue open circles, and extended objects as red dots. Long-dashed lines correspond to the CS and R_1/2 cuts adopted in this work. In the top and right panels, we plot the normalised distributions of R_1/2 and CS, respectively (short dashed line for saturated sources, long dashed line for blended stars, and red solid line for extended objects).