N_H-redshift distribution of all the objects in the catalog. Up- and right-pointing arrows show the redshift and N_H lower limits for objects with a flat photometric redshift probability curve. Upper limits are shown as down-pointing triangles. The spectral types are color-coded: red, NL-AGN, blue, BL-AGN, yellow, Early Type Galaxies, aquamarine, Emission Line Galaxies, gray, no spectral identification