Oxygen abundances in the narrow line regions of Seyfert galaxies and the metallicity-luminosity relation

We present oxygen abundances relative to hydrogen (O/H) in the narrow line regions (NLRs) gas phases of Seyferts 1 (Sy 1s) and Seyferts 2 (Sy 2s) active galactic nuclei (AGNs). We used fluxes of the optical narrow emission line intensities [3 500 < lambda( A) < 7 000] of 561 Seyfert nuclei in the local Universe ( z ? 0.31) from the second catalogue and data release (DR2) of the BAT AGN Spectroscopic Surv e y, which focuses on the Swift-BAT hard X-ray (> 10 keV) detected AGNs. We derived O/H from relative intensities of the emission lines via the strong-line methods. We find that the AGN O/H abundances are related to their hosts stellar masses and that they follow a downward redshift evolution. The derived O/H together with the hard X-ray luminosity (L-X) were used to study the X-ray luminosity-metallicity (L-X-Z(NLR)) relation for the first time in Seyfert galaxies. In contrast to the broad-line focused (L-X-Z(BLR)) studies, we find that the L-X -Z(NLR) exhibit significant anticorrelations with the Eddington ratio (lambda(Edd)) and these correlations vary with redshifts. This result indicates that the low-luminous AGNs are more actively undergoing interstellar medium enrichment through star formation in comparison with the more luminous X-ray sources. Our results suggest that the AGN is somehow driving the galaxy chemical enrichment, as a result of the inflow of pristine gas that is diluting the metal rich gas, together with a recent cessation on the circumnuclear star-formation.