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

TL;DR

This study analyzes the distribution of heavy elements in the extended narrow line region of Seyfert galaxy NGC 7212, revealing shock velocities, elemental depletions, and emission mechanisms through spectral modeling.

Contribution

It provides detailed modeling of the ENLR in NGC 7212, including shock velocities, elemental abundances, and emission processes, advancing understanding of Seyfert galaxy environments.

Findings

High shock velocities (500-800 km/s) at the edges of the cone.

Elemental depletion patterns, especially for nitrogen, sulphur, and oxygen.

Detection of radio synchrotron and X-ray emission mechanisms.

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 accounting for photoionization from the active nucleus and shocks. The results show that relatively high (500--800 \kms) shock velocities appear on the edge of the cone and outside of it. 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, and less so for Seyfert 2 galaxies. The preshock densities are characteristic of the ENLR and range between 80--150 cm$^{-3}$. Nitrogen and sulphur are found 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.