Forbidden lines in quasars and active galaxies

We consider the effects of photoexcitation and photoionization from the metastable levels of ions in the high radiation environments expected in the nuclei of Seyfert galaxies, broad-line radio galaxies, and quasars. Anomalous line ratios in the narrow-line components and the absence of forbidden lines in the broad-line components of these objects may result from proximity of the emitting region to the central UV source, and do not necessarily imply high electron densities. Detailed calculations are presented for the case of [O III]