Semi-empirical metallicity calibrations based on ultraviolet emission lines of type-2 AGNs

Abstract

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$1240/He II$\lambda 1640$, C43=log[(C IV$\lambda 1549$+C III]$\lambda 1909$)/HeII$\lambda 1640$] and C III]$\lambda 1909$/C IV$\lambda 1549$ emission-line intensity ratios. A metallicity-independent calibration between the ionization parameter and the C III]$\lambda 1909$/C IV$\lambda 1549$ 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.

15 pages, MNRAS accepted

References in corpus (18)

• The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2
• Emission-line Diagnostics of Low Metallicity AGN
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• Keck HIRES Spectroscopy of Extragalactic HII Regions: C and O Abundances from Recombination Lines
• On the abundance discrepancy problem in HII regions
• The localized chemical pollution in NGC 5253 revisited: Results from deep echelle spectrophotometry
• IZI: Inferring the Gas Phase Metallicity (Z) and Ionization Parameter (q) of Ionized Nebulae using Bayesian Statistics
• Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution
• [ArIII]/[OIII] and [SIII]/[OIII]: well-behaved oxygen abundance indicators for HII regions and star forming galaxies
• Metallicity evolution of AGNs from UV emission-lines based on a new index
• Metallicity calibrations for diffuse ionised gas and low ionisation emission regions
• The mass-metallicity relation of local active galaxies
• New metallicity calibration for Seyfert 2 galaxies based on the N2O2 index
• Carbon and Nitrogen Abundance Ratio In the Broad Line Region of Tidal Disruption Events
• Modelling narrow-line regions of active galaxies in the Sloan Digital Sky Survey - I.Sample selection and physical conditions
• Imaging and Spectroscopy of Ultra Steep Spectrum Radio Sources
• Using photo-ionisation models to derive carbon and oxygen gas-phase abundances in the rest UV
• Chemical evolution of the Universe at 0.7 < z < 1.6 derived from abundance diagnostics of the broad-line region of quasars

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• MUSE Analysis of Gas around Galaxies (MAGG) -- III: The gas and galaxy environment of z = 3-4.5 quasars
• Chemical abundances of Seyfert 2 AGNs I. Comparing oxygen abundances from distinct methods using SDSS
• Chemical abundances in Seyfert galaxies -- V. The discovery of shocked emission outside the AGN ionization axis
• Metallicity in Quasar Broad Line Regions at Redshift $\sim$ 6
• Optical and mid-infrared line emission in nearby Seyfert galaxies
• Chemical Abundance of z~6 Quasar Broad-Line Regions in the XQR-30 Sample
• Chemical abundances of Seyfert 2 AGNs IV. Composite models calculated by photoionization + shocks
• Gas phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA: evidence of metal poor accretion
• Oxygen abundances in the narrow line regions of Seyfert galaxies and the metallicity-luminosity relation
• Measuring chemical abundances in AGN from infrared nebular lines: HII-CHI-Mistry-IR for AGN
• The mass-metallicity and fundamental metallicity relations in non-AGN and AGN-host galaxies
• Chemical abundances in Seyfert galaxies X. Sulphur abundance estimates
• Chemical Abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA
• Cosmic Ray Ionization of Low-Excitation Lines in Active Galactic Nuclei and Starburst Galaxies
• Polycyclic aromatic hydrocarbons and the ionized gas
• Assessing model-based carbon and oxygen abundance derivation from ultraviolet emission lines in AGNs
• Exploring the hardness of the ionizing radiation with the infrared softness diagram. II. Bimodal distributions in both the ionizing continuum slope and the excitation in active galactic nuclei
• Chemical abundances in Seyfert galaxies -- VII. Direct abundance determination of neon based on optical and infrared emission lines