Publication Date:
2020-02-03
Description:
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 $0.3 : lesssim : (Z/{
m Z}_{odot }) : lesssim : 2.0$ that corresponds to $-0.7 : lesssim : ({
m N}2) : lesssim : 0.6$. 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.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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