Semi-empirical metallicity calibrations based on ultraviolet emission lines of type-2 AGNs. (arXiv:1905.00691v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dors_O/0/1/0/all/0/1">O. L. Dors</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monteiro_A/0/1/0/all/0/1">A. F.Monteiro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cardaci_M/0/1/0/all/0/1">M. V. Cardaci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hagele_G/0/1/0/all/0/1">G. F. Hagele</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Krabbe_A/0/1/0/all/0/1">A. C. Krabbe</a>

We derived two semi-empirical calibrations between the metallicity of the
Narrow Line Region (NLR) of type-2 Active Galactic Nuclei and the rest-frame of
the N V$lambda$1240/He II$lambda1640$, C43=log[(C IV$lambda1549$+C
III]$lambda1909$)/HeII$lambda1640$] and C III]$lambda1909$/C IV$lambda1549$
emission-line intensity ratios. A metallicity-independent calibration between
the ionization parameter and the C III]$lambda1909$/C IV$lambda1549$
emission-lines ratio was also derived. These calibrations were obtained
comparing ratios of measured UV emission-line intensities, compiled from the
literature, for a sample of 77 objects (redshift $0 : < : z : < : 3.8$) with those predicted by a grid of photoionization models built with the Cloudy code. Using the derived calibrations, it was possible to show that the metallicity estimations for NLRs are lower by a factor of about 2-3 than those for Broad Line Regions (BLRs). Besides we confirmed the recent result of the existence of a relation between the stellar mass of the host galaxy and its NLR metallicity. We also derived a $M-Z$ relation for the objects in our sample at $1.6 : < : z : < : 3.8$. This relation seems to follow the same trend as the ones estimated for Star Forming galaxies of similar high redshifts but for higher masses.

We derived two semi-empirical calibrations between the metallicity of the
Narrow Line Region (NLR) of type-2 Active Galactic Nuclei and the rest-frame of
the N V$lambda$1240/He II$lambda1640$, C43=log[(C IV$lambda1549$+C
III]$lambda1909$)/HeII$lambda1640$] and C III]$lambda1909$/C IV$lambda1549$
emission-line intensity ratios. A metallicity-independent calibration between
the ionization parameter and the C III]$lambda1909$/C IV$lambda1549$
emission-lines ratio was also derived. These calibrations were obtained
comparing ratios of measured UV emission-line intensities, compiled from the
literature, for a sample of 77 objects (redshift $0 : < : z : < : 3.8$)
with those predicted by a grid of photoionization models built with the Cloudy
code. Using the derived calibrations, it was possible to show that the
metallicity estimations for NLRs are lower by a factor of about 2-3 than those
for Broad Line Regions (BLRs). Besides we confirmed the recent result of the
existence of a relation between the stellar mass of the host galaxy and its NLR
metallicity. We also derived a $M-Z$ relation for the objects in our sample at
$1.6 : < : z : < : 3.8$. This relation seems to follow the same trend as
the ones estimated for Star Forming galaxies of similar high redshifts but for
higher masses.

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