Chemical abundances of Seyfert 2 AGNs - I

The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass-metallicity relation of active galactic nuclei (AGNs) at low redshifts (z~<0.4). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPAC Extragalactic Database (NED) to selected optical (3000<{lambda}({AA})<7000) emission line intensities of 463 confirmed Seyfert 2 AGNs.

The oxygen abundances of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the Bayesian HII-CHI-MISTRY code and the Te-method. We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ~0.8dex, with the largest discrepancies in the low-metallicity regime (12+log(O/H)~<8.5). We confirmed that the Te-method underestimates the oxygen abundance in NLRs, producing unreal subsolar values.