Notes. Fluxes are in units of 10⁻¹⁵ erg s⁻¹ cm⁻² and they were divided by a factor (1+z) because they were measured in the rest-frame spectra shown in Fig. 2. We fitted the three emission lines with three Gaussian components plus a linear polynomial to describe the local continuum, using the lmfit package. The last two rows correspond to upper limits on the electron densities measured from [Ne V]14.3/24.3+Δ[Ne V]14.3/24.3 using PyNeb (v1.1.19) and considering electron temperatures of 10⁴ and 2×10⁴ K. For reference, the median values of [Ne III]/[Ne II] and [Ne V]/[Ne II] reported by Pereira-Santaella et al. (2010) for QSOs, Seyfert 1, Seyfert 2 galaxies, and LINERs measured from Spitzer/IRS spectra are shown in Fig. 3. The median [Ne V]14.3/24.3 values reported for the same groups are 1.00±0.30, 0.91±0.25, 1.00±0.30, and 0.77±0.18.