1. Empirical calibration for helium abundance determinations in active galactic nuclei.
- Author
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Dors, O L, Almeida, G C, Oliveira, C B, Flury, S R, Riffel, R, Riffel, R A, Cardaci, M V, Hägele, G F, Ilha, G S, Krabbe, A C, Arellano-Córdova, K Z, Santos, P C, and Morais, I N
- Subjects
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ACTIVE galactic nuclei , *ACTIVE galaxies , *ELECTRON temperature , *CALIBRATION , *HELIUM - Abstract
For the first time, a calibration between the He i |$\lambda 5876$| /H |$\beta$| emission line ratio and the helium abundance y = 12 + log(He/H) for Narrow line regions of Seyfert 2 Active Galactic Nuclei is proposed. In this context, observational data (taken from the SDSS-DR15 and from the literature) and direct abundance estimates (via the |$T_{\rm e}$| -method) for a sample of 65 local (|$z \: \lt \: 0.2$|) Seyfert 2 nuclei are considered. The resulting calibration estimates the y abundance with an average uncertainty of 0.02 dex. Applying our calibration to spectroscopic data containing only strong emission lines, it yields a helium abundance distribution similar to that obtained via the |$T_{\rm e}$| -method. Some cautions must be considered to apply our calibration for Seyfert 2 nuclei with high values of electron temperature (|${\gtrsim} 20\, 000$| K) or ionization parameter (|$\log U \ \gt\ {-}2.0$|). [ABSTRACT FROM AUTHOR]
- Published
- 2024
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