Chemical abundances of Seyfert 2 AGNs - II. N2 metallicity calibration based on SDSS
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 ≲ 0.4) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z-N2 relation is valid for the range 0.3 ≲ (Z/Z_{⊙ }) ≲ 2.0 that corresponds to -0.7 ≲ (N2) ≲ 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2020
- DOI:
- 10.1093/mnras/staa193
- arXiv:
- arXiv:2001.07126
- Bibcode:
- 2020MNRAS.492.5675C
- Keywords:
-
- galaxies: abundances;
- galaxies: active;
- galaxies: evolution;
- galaxies: formation;
- galaxies: ISM;
- galaxies: nuclei;
- galaxies: Seyfert;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 10 pages, 6 figuras, accepted for publication in MNRAS