On the central abundances of active galactic nuclei and star-forming galaxies

DORS, O.L.; CARDACI, M.V.; HÄGELE, G.F.; RODRIGUES, I.; GREBEL, E.K.; PILYUGIN, L.S.; FREITAS-LEMES, P.; KRABBE, A. C.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2015 vol. 453 p. 4102 - 4111

0035-8711

We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active galactic nuclei (AGNs) estimated from the optical emission lines through the strong-line method, via the direct Te-method, and the central intersect abundances in the host galaxies determined from the radial abundance gradients. We found that the Te-method underestimates the oxygen abundances by up to ~2 dex (with averaged value of ~0.8 dex) compared to the abundances derived through the strong-line method. This confirms the existence of the so-called `temperature problem´ in AGNs. We also found that the abundances in the centres of galaxies obtained from their spectra trough the strong-line method are close to or slightly lower than the central intersect abundances estimated from the radial abundance gradient both in AGNs and star-forming galaxies. The oxygen abundance of the NLR is usually lower than the maximum attainable abundance in galaxies (?2 times the solar value). This suggests that there is no extraordinary chemical enrichment of the NLRs of AGNs.