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

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 T e-method, and the central intersect abundances in the host galaxies determined from the radi...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2015-11, Vol.453 (4), p.4102-4111
Main Authors: Dors, O. L., Cardaci, M. V., Hägele, G. F., Rodrigues, I., Grebel, E. K., Pilyugin, L. S., Freitas-Lemes, P., Krabbe, A. C.
Format: Article
Language:English
Subjects:
Abundance
Active galactic nuclei
Astronomical bodies
Astronomy
Emission
Enrichment
Galaxies
Oxygen
Spectra
Star & galaxy formation
Star formation
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Summary: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 T e-method, and the central intersect abundances in the host galaxies determined from the radial abundance gradients. We found that the T e-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.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stv1916