Chemical abundances of Seyfert 2 AGNs – II. N2 metallicity calibration based on SDSS. Issue 4 (3rd February 2020)

• Record Type: Journal Article
• Authors: Carvalho, S P; Dors, O L; Cardaci, M V; Hägele, G F; Krabbe, A C; Pérez-Montero, E; Monteiro, A F; Armah, M; Freitas-Lemes, P
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 492:Issue 4(2020)
• Page Start: 5675
• Page End: 5683
• Publication Date: 2020-02-03
• Subjects: galaxies: abundances -- galaxies: active -- galaxies: evolution -- galaxies: formation -- galaxies: ISM -- galaxies: nuclei -- galaxies: Seyfert; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa193
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present a semi-empirical calibration between the metallicity ( Z ) of Seyfert 2 active galactic nuclei and the N2 = log([N ii ]λ6584/H α) emission-line intensity ratio. This calibration was derived through the [O iii ]λ5007/[O ii ]λ3727 versus N2 diagram containing observational data and photoionization model results obtained with the cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift $z \: \lesssim 0.4$ ) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z –N2 relation is valid for the range $0.3 \: \lesssim \: (Z/{\rm Z}_{\odot }) \: \lesssim \: 2.0$ that corresponds to $-0.7 \: \lesssim \: ({\rm N}2) \: \lesssim \: 0.6$ . The effects of varying the ionization parameter ( U ), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z –N2 calibration. A relation between U and the [O iii ]/[O ii ] line ratio, almost independent of other nebular parameter, was obtained.