Chemical abundances in Seyfert galaxies – VII. Direct abundance determination of neon based on optical and infrared emission lines. Issue 1 (16th September 2021)

• Record Type: Journal Article
• Authors: Armah, Mark; Dors, O L; Aydar, C P; Cardaci, M V; Hägele, G F; Feltre, Anna; Riffel, R; Riffel, R A; Krabbe, A C
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 508:Issue 1(2021)
• Page Start: 371
• Page End: 391
• Publication Date: 2021-09-16
• Subjects: ISM: abundances -- galaxies: abundances -- galaxies: active -- galaxies: evolution -- galaxies: nuclei -- galaxies: Seyfert; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab2610
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: For the first time, neon abundance has been derived in the narrow line region from a sample of Seyfert 2 nuclei. In view of this, we compiled from the literature fluxes of optical and infrared (IR) narrow emission lines for 35 Seyfert 2 nuclei in the local universe ($z \:\lesssim \:0.06$ ). The relative intensities of emission lines were used to derive the ionic and total neon and oxygen abundances through electron temperature estimations ( T e -method). For the neon, abundance estimates were obtained by using both T e -method and IR-method. Based on photoionization model results, we found a lower electron temperature [$t_{\rm e}({\rm Ne\, \small {III}})$ ] for the gas phase where the Ne 2 + is located in comparison with t 3 for the O 2 + ion. We find that the differences (D) between Ne 2 + /H + ionic abundances calculated from IR-method and T e -method (assuming t 3 in the Ne 2 + /H + derivation) are similar to the derivations in star-forming regions (SFs) and they are reduced by a mean factor of ∼3 when $t_{\rm e}({\rm Ne\, \small {III}})$ is considered. We propose a semi-empirical Ionization Correction Factor (ICF) for the neon, based on [Ne ii ]12.81$\rm{\mu m}$, [Ne iii ]15.56$\rm{\mu m}$, and oxygen ionic abundance ratios. We find that the average Ne/H abundance for the Seyfert 2s sample is nearly 2 times higher than similar estimate for SFs. Finally, for the very high metallicity regime (i.e. [$\rm 12+log(O/H)\: \gtrsim \: 8.80$ ]) an increase in Ne/O with O/H is found, which likely indicates secondary stellar production for the neon.