Emission-line diagnostics and photoionization modeling of Jil’s spectrum. In all panels we show CLOUDY (Ferland et al. 2013) photoionization model results for an obscured AGN with three different fractions of the LBQS 0302–0019 UV luminosity, three metallicities, and a range of ionization parameters U as indicated in the legend and color bar of the middle panel. Left: He II/Lyα vs. C IV/Lyα of Jil 20 kpc from LBQS 0302–0019 (red filled circle) in comparison to various measurements of other Lyα nebulae around QSOs, radio galaxies, and obscured AGN at z > 2 (see legend). Middle: C IV/He II vs. C III/C IV diagnostic diagram with symbols as in the left panel. Right: ratio of observed to predicted He II luminosity as a function of the radius of a He II emitting sphere. Illumination by LBQS 0302–0019 results in the black solid line.