B − z vs z − K plot of all GMASS objects. Closed symbols represent objects with secure spectroscopic redshifts. For the remaining (open) symbols, the photometric redshift is used. Upward pointing triangles indicate z > 1.4; these are grey [red] for the range 1.4 < z ≤ 2.5 and black for z > 2.5. Downward pointing (blue) triangles z ≤ 1.4 and (black) stars indicate z = 0 (i.e., stars). No special effort has been undertaken to identify stars based on their spatial appearance, hence most downward pointing symbols in the stellar region will indeed be stars. The limits of the BzK selection are indicated by dashed lines.