From top to bottom, first and second panels: logarithm of the luminosities of the extended ELRs in the [N II] line vs. nuclear line luminosity and radio luminosities (all quantities in erg s⁻¹). Sources are coded with symbols combining the optical spectroscopic classification and radio morphology. The dashed line is the bisectrix of the plane. Third panel: luminosity of the Hα+[N II] emission line vs. redshift. Fourth panel: logarithm of the size of the extended ELR (in kpc) vs. nuclear line luminosity. The dashed line shows the relation.