Figure 2.
![Line ratio as a function of the gas metallicity for a 100 kK blackbody (top) and an AGN SED (bottom). The dashed line indicates the upper observational limit of C iii] 1908 Å/He ii < 0.4 and the three different lines represent different ionization parameters of the gas. For metallicities below ∼10−2, all models are in agreement with the observation.](https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/mnras/462/2/10.1093_mnras_stw1775/2/stw1775fig2.jpeg?Expires=1750561944&Signature=U2D6WMLgItJNIW8qn5vDVANgi~8gWSvX4V0Wq6G0y6vxGQE1Da1CrwUuSNI8AK-9wDeqXPuszpTN8AKNznB3srI5DYeWlLoSNex-t4a~BnAFFzkLjUfsx0yvBqK6v1LH4GPX6b32yfn8Kt0Q7UFnx7MWvN4rZCNOkegfhqkFAM-vcBWqnxRf9MMiDG0xLVr~5Q8V~B-9S-P5SxWlWuQQV7nCo~kDQnv3dHJ7snk6tctXNumA59SnZxKUI0YMBypirxyHzIRTKA8gBiEfnoN8k7Kbtflu42UfIpOgcdymJjQ5bXyg7V9uSyjnvzGgY~6vZnvxQ3i6tP20VbmFYxlvTQ__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Line ratio as a function of the gas metallicity for a 100 kK blackbody (top) and an AGN SED (bottom). The dashed line indicates the upper observational limit of C iii] 1908 Å/He ii < 0.4 and the three different lines represent different ionization parameters of the gas. For metallicities below ∼10−2, all models are in agreement with the observation.
