Hardness ratio as function of hard (2–10 keV) X-ray luminosity. Vertical dashed lines show the typical separation for AGNs and quasars used in the X-rays. The horizontal line shows the limit values for obscured and unobscured AGNs in the X-rays. Stars and ‘X’ symbols indicate obscured and unobscured AGNs with high-excitation values (log([O III]λ5007/Hβ) > 0.5). Sources marked with green circles correspond to X-ray emitters found in the region of the MEx diagram that is generally associated with star-forming galaxies. Vertical colour bar shows the corresponding log(N_H) values.