Abundance analysis of 84 type-2 AGNs finds oversolar He and subsolar O at z>2.8, including one object at z=6.26 with record He abundance of 12+log(He/H)=11.64, plus marginal trends of declining He/H and rising O/H toward z=0.
A grid of composite models for the simulation of the emission-line spectra from the NLR of active galaxies
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abstract
A grid of composite models for the narrow line region of active galaxies, which consistently account for both the effect of a photoionizing radiation from the active center and of a shock front, is presented. Theoretical results, calculated with the SUMA code, are given for different values of shock velocities, preshock densities, geometrical thickness of the clouds, and, particularly, for the ionizing radiation intensity in a large range. The input parameters are chosen within the ranges indicated by previous fits of several observed emission-line and continuum spectra from active galaxies. Shock velocities from 100 \kms ~to 1500 \kms ~and preshock densities from 100 \cm3 to 1000 \cm3 are considered. The line intensities of the most important ultraviolet, optical and infrared transitions are obtained and are listed in several tables.
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Cosmic evolution of the helium and oxygen abundances in type 2 Active Galactic Nuclei: Helium-loud AGNs
Abundance analysis of 84 type-2 AGNs finds oversolar He and subsolar O at z>2.8, including one object at z=6.26 with record He abundance of 12+log(He/H)=11.64, plus marginal trends of declining He/H and rising O/H toward z=0.