The origin of gas in the Extended Narrow Line Region of nearby Seyfert
  galaxies.I. NGC 7212
  The Extended Narrow Line Region (ENLR) of Active Galactic Nuclei (AGN) is a
region of highly ionized gas with a size of few up to 15-20 kpc. When it shows
a conical or bi-conical shape with the apexes pointing towards the active
nucleus, this region is also called ionization cones. The ionization cones are
an evidence of the Unified Model that predicts an anisotropic escape of
ionizing photons from the nucleus confined to a cone by a dusty torus. Many
details about the complex structure of the ENLR still remain unveiled, as for
example the origin of the ionized gas. Here we present new results of a study
of the physical and kinematical properties of the circumnuclear gas in the
nearby Seyfert 2 galaxy NGC 7212. Medium and high resolution integral field
spectra and broad-band photometric data were collected and analysed in the
frame of an observational campaign of nearby Seyfert galaxies, aiming to handle
the complicated issue of the origin of the gas in the ENLR. This work is based
on: (i) analysis of gas physical properties (density, temperature and
metallicity), (ii) analysis of emission line ratios, and (iii) study of
kinematics of gas and stars. By reconstructing the [O III]/Hbeta ionization
map, we pointed out for the first time the presence of an ionization cone
extended up to about 6 kpc, made by a large amount of low metallicity gas,
kinematically disturbed and decoupled from stars, whose highly ionized
component shows radial motions at multiple velocities proved by the complex
profiles of the specral lines. Since NGC 7212 is a strongly interacting triple
galaxy system, the gravitational effects are likely to be at the origin of the
ENLR in this Seyfert galaxy.
