BPT diagram of our sources with two of the models of Kewley et al. (2013a) shown for z = 2.5. Red circles show the 25 radio galaxies from the present analysis and those of Collet et al. (2016), which have measurements of all four lines or sensitive upper limits (on Hβ or [NII]λ6583). We also mark the range of line ratios expected for low-redshift galaxies with ordinary star formation properties and high-metallicity AGN narrow-line regions (light blue hatched region). The red lines show the “high-redshift” starburst region of Kewley et al. (2013a) and the AGN branch with low-metallicity narrow-line regions (their scenario 4).