Position in the CIV(EW) vs. HeII(EW) plane of models with 40% (crosses), 60% (triangles) and 100% (circles) contribution to the observed UV emission of the two BDF galaxies from narrow-line AGN (from Feltre et al. 2016) with different metallicities and ionization parameters. Symbols at increasing sizes are for models with Z = 0.025, 0.1, 0.4 Z_⊙, whose colour indicate the relevant ionization parameter log(U_s). The shaded regions highlight the parameter space allowed at 1σ, 2σ, and 3σ by the X-shooter observations of BDF521 (top) and BDF2195 (bottom).