Distribution of the heavy elements throughout the extended narrow-line region of the Seyfert galaxy NGC 7212^⋆

¹ Dipartimento di Fisica e AstronomiaUniversity of Padova, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
e-mail: valentina.cracco@unipd.it
² School of Physics and Astronomy, Tel-Aviv University, 69978 Tel-Aviv, Israel

Received: 7 March 2012
Accepted: 4 July 2012

Abstract

The latest observations of line and continuum spectra emitted from the extended narrow-line region (ENLR) of the Seyfert 2 galaxy NGC 7212 are analysed using models that account for photoionization from the active galactic nucleus (AGN) and shocks. The results show that relatively high (500–800 km s^-1) shock velocities appear at the edge of the cone and beyond. The model-inferred AGN flux, which is lower than 10^-11 photons cm^-2 s^-1 eV^-1 at the Lyman limit, is more typical of low-luminosity AGN than Seyfert 2 galaxies. The preshock densities are characteristic of the ENLR and range between 80–150 cm^-3. Nitrogen and sulphur are found to be depleted by a factor lower than 2, particularly at the eastern edge. Oxygen is depleted at several locations. The Fe/H ratio is approximately solar, whereas the Ne/H relative abundance is unusually high, 1.5–2 times the solar value. Modelling the continuum spectral energy distribution (SED), we have found radio synchrotron radiation generated by the Fermi mechanism at the shock front, whereas the X-rays are produced by the bremsstrahlung from a relatively high temperature plasma.