The following document lists the file abstract/EOLIVA_ZZCORLIN.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
This is a solicited proposal following up GT spectral observations of an handful of active galaxies, mostly type 2 Seyferts, which show prominent lines from highly ionized species OIV, NeV, NeVI, MgVII, MgVIII, SiIX. These coronal lines can be used both to determine the physical conditions (e.g. ionization mechanism, abundances) of the coronal line region, and to constrain the shape of the AGN ionizing spectrum (20-200 eV) by means of photoionization models. Preliminary results indicate that type 2 Seyferts have a prominent UV bump peaking at about 70 eV (Moorwood et al. 1996), and its strength relative to the underlying power-law continuum may vary between different objects. One of the most puzzling results is that the only Seyfert 1 so far observed (NGC4151) displays a much lower degree excitation, i.e. progressively weaker lines from higher ionization species. This may indicate an intrinsic difference between the ionizing spectra of type 1 and 2 Seyferts, i.e. that the popular unified models for AGNs could be incorrect. Verifying this possibility is the main aim of this proposal where we plan SWS observations of 4 bona fide Seyfert 1 galaxies which should provide a large enough sample to check for systematic differences between the two Seyfert types.