Zoomed-in spectral regions of the nuclear spectra around the wavelengths of high-excitation lines [Mg V] (top) and [Ne V] (bottom). The black lines are the observed spectra extracted with an aperture radius of 0.5″ (top) and an aperture radius of 1″ (bottom), while the dotted and dashed lines are the predicted high-excitation emission lines from MRS observations of two local AGN assuming an intrinsic 2 − 10 keV luminosity of 10⁴⁴ erg s⁻¹ for Mrk 231 (see text for details). The ch3-medium spectrum was corrected for residual fringing that was affecting mostly data at wavelengths longer than that of [Ne V].