Temperature Discrepancy with Photoionization Models of the Narrow Line
  Region
  Using published work on the Narrow Line Region of Active Nuclei, we make a
comparison of the observed [O III] $4363\AA/5007\AA$ ratio observed among
quasars, Seyfert 2's and spatially resolved NLR plasma. It is broadly accepted
that the span of this ratio among quasars, from 0.015 to 0.2, is the result of
collisional deexcitation as corroborated by Baskin and Laor (2005). However,
the coincidence of the AGN at towards the lowest [O III] ratios, however,
suggests that it represents plasma in the low density regime, where this ratio
can be interpreted as the actual NLR temperature. Using the density indicator
[Ar IV] $4711\AA/4740\AA$ doublet ratio which was observed by Koski (1978) in
Seyfert 2's, we found evidence of relatively low densities ($< 10000/cc$). Even
after considering a powerlaw distribution for the densities as well as a
nonuniform foreground dust extinction, we find no evidence of collisional
deexcitation. The mean NLR OIII temperature we infer for our Seyfert 2 sample
is 13,500 K. This is a problem for photoionization models with a standard
ionizing spectral energy distribution since they predict significantly lower
temperatures.
