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arXiv · 2302.12876

Chemical abundances in Seyfert galaxies X. Sulphur abundance estimates

O. L. Dors·M. Valerdi·R. A. Riffel·R. Riffel·M. V. Cardaci·G. F. Hägele·M. Armah·M. Revalski·S. R. Flury·P. Freitas-Lemes·E. B. Amôres·A. C. Krabbe·L. Binette·A. Feltre·T. Storchi-Bergmann
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Abstract

For the first time, the sulphur abundance relative to hydrogen (S/H) in the Narrow Line Regions of a sample of Seyfert 2 nuclei (Sy 2s) has been derived via direct estimation of the electron temperature. Narrow emission line intensities from the SDSS DR17 [in the wavelength range 3000 < $\lambda$ < 9100] and from the literature for a sample of 45 nearby ($z$ < 0.08) Sy 2s were considered. Our direct estimates indicate that Sy 2s have similar temperatures in the gas region where most of the S+ ions are located in comparison with that of star-forming regions (SFs). However, Sy 2s present higher temperature values ($\sim$10000 K) in the region where most of the S++ ions are located relative to that of SFs. We derive the total sulphur abundance in the range of 6.2 < 12 + log(S/H) < 7.5, corresponding to 0.1-1.8 times the solar value. These sulphur abundance values are lower by $\sim$0.4 dex than those derived in SFs with similar metallicity, indicating a distinct chemical enrichment of the ISM for these object classes. The S/O values for our Sy 2 sample present an abrupt ($\sim$0.5 dex) decrease with increasing O/H for the high metallicity regime [12 + log(O/H) > 8.7)], what is not seen for the SFs. However, when our Sy 2 estimates are combined with those from a large sample of star-forming regions, we did not find any dependence between S/O and O/H.

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O. L. Dors, M. Valerdi, R. A. Riffel, R. Riffel, M. V. Cardaci, G. F. Hägele, M. Armah, M. Revalski, S. R. Flury, P. Freitas-Lemes, E. B. Amôres, A. C. Krabbe, L. Binette, A. Feltre, T. Storchi-Bergmann. 2023-02-24. Chemical abundances in Seyfert galaxies X. Sulphur abundance estimates. https://doi.org/10.1093/mnras/stad635

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