We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 Active Galactic Nuclei and the N 2=log([N ii]λ6584/Hα) emission-line intensity ratio. This calibration was derived through the [O iii]λ5007/[O ii]λ3727 versus N 2 diagram containing observational data and photoionization model results obtained with the Cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift z 0.4) taken from the Sloan Digital Sky Survey DR7 dataset. The obtained Z-N 2 relation is valid for the range 0.3 (Z/Z ⊙ ) 2.0 which corresponds to −0.7 (N 2) 0.6. The effects of varying the ionization parameter (U ), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N 2. This result indicates the large reliability of our Z − N 2 calibration. A relation between U and the [O iii]/[O ii] line ratio, almost independent of other nebular parameter, was obtained.

We investigate interaction effects in the stellar and gas kinematics, stellar population, and ionized gas properties of the interacting galaxy pair AM 1204−292,composed of NGC 4105 and NGC 4106. The data consist of long-slit spectra in the range 3000–7050 Å. The massive E3 galaxy NGC 4105 presents a flat stellar velocity profile, while the ionized gas is in strong rotation, suggesting an external origin. Its companion, NGC 4106, shows asymmetries in the radial velocity field, likely due to the interaction. The dynamics of the interacting pair were modelled using the P-Gadget3 treepm/sph code, from which we show that the system has just passed the first perigalacticum, which triggered an outbreak of star formation, currently at full maximum. We characterized the stellar population properties using the stellar population synthesis code starlight and, on average, both galaxies are predominantly composed of old stellar populations. NGC 4105 has a slightly negative age gradient, comparable with that of the most massive elliptical galaxies, but a steeper metallicity gradient. The SB0 galaxy NGC 4106 presents smaller radial variations in both age and metallicity in comparison with intermediate-mass early-type galaxies. These gradients have not been disturbed by interaction, since the star formation happened very recently and was not extensive in mass. Electron density estimates for the pair are systematically higher than those obtained in isolated galaxies. The central O/H abundances were obtained from photoionization models in combination with emission-line ratios, which resulted in 12 + log(O/H) = 9.03 ± 0.02 and 12 + log(O/H) = 8.69 ± 0.05 for NGC 4105 and NGC 4106, respectively.