Electron Energy Distributions in the Extended Gas Nebulae associated
  with High-z AGN: Maxwell-Boltzmann vs. kappa distributions
  Emission line observations together with photoionization models provide
important information about the ionization mechanisms, densities, temperatures,
and metallicities in AGN-ionized gas. Photoionization models usually assume
Maxwell-Boltzmann (M-B) electron energy distributions (EED), but it has been
suggested that using kappa distributions may be more appropriate and could
potentially solve the discrepancies in temperatures and abundances found in HII
regions and Planetary Nebulae (PNe). We consider the impact of the presence of
kappa distributions in photoionized nebulae associated with AGN and study how
this might affect spectral modelling and abundance analyses for such regions.
Using the photoionization code MAPPINGS 1e we compute models adopting M-B and
kappa distributions of electron energies, and compare the behaviour of emission
line ratios for different values of kappa, gas metallicity, density, ionization
parameter and SED slope. We find that the choice of EED can have a large impact
on some UV and optical emission lines emitted by photoionized nebulae
associated with AGN, and that the impact of adopting a kappa distribution is
strongly dependent on gas metallicity and ionization parameter. We compile a
sample of line ratios for 143 type 2 AGN and compare our models against the
observed line ratios. We find that for 98 objects kappa distributions provide a
better fit to the observed line ratios than M-B distributions. In addition, we
find that adopting kappa-distributed electron energies results in significant
changes in the inferred gas metallicity and ionization parameter in a
significant fraction of objects.
