A bayesian-like approach to derive chemical abundances in Type-2 Active
  Galactic Nuclei based on photoionization models
  We present a new methodology for the analysis of the emission lines of the
interstellar medium in the Narrow Line Regions around type-2 Active Galactic
Nuclei. Our aim is to provide a recipe that can be used for large samples of
objects in a consistent way using different sets of optical emission-lines that
takes into the account possible variations from the (O/H)-(N/O) relation to use
[N II] lines. Our approach consists of a bayesian-like comparison between
certain observed emission-line ratios sensitive to total oxygen abundance,
nitrogen-to-oxygen ratio and ionization parameter with the predictions from a
large grid of photoionization models calculated under the most usual conditions
in this environment. We applied our method to a sample of Seyfert 2 galaxies
with optical emission-line fluxes and determinations of their chemical
properties from detailed models in the literature. Our results agree within the
errors with other results and confirm the high metallicity of the objects of
the sample, with N/O values consistent wit a large secondary production of N,
but with a large dispersion. The obtained ionization parameters for this sample
are much larger than those for star-forming object at the same metallicity.
