| Full text | |
| Author(s): Show less - |
Dors, O. L.
;
Oliveira, C. B.
;
Cardaci, M., V
;
Hagele, G. F.
;
Morais, I. N.
;
Ji, X.
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Riffel, R. A.
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Riffel, R.
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Mezcua, M.
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Almeida, G. C.
;
Santos, P. C.
;
de Mellos, M. S. Z.
Total Authors: 12
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| Document type: | Journal article |
| Source: | Monthly Notices of the Royal Astronomical Society; v. 540, n. 2, p. 18-pg., 2025-06-01. |
| Abstract | |
Metallicity (Z) estimates based on ultraviolet (UV) emission lines from the narrow-line regions of active galactic nuclei (AGNs) have been found to differ from those derived from optical lines. However, the origin of this discrepancy (ZR) remains poorly understood. To investigate the source of ZR, we compiled from the literature the fluxes of narrow near-UV [1000<lambda(A & ring;)<2000] and optical [3000<lambda(A & ring;)<7000] emission-line measurements for a sample of 11 AGNs (nine at z<0.4 and two at z similar to 2.4). Metallicity values for our sample were derived using a semi-empirical calibration based on the C43 = log[(C iv lambda 1549 + C iii]lambda 1909)/He ii lambda 1640] emission-line ratio and compared with those obtained via direct measurement of the electron temperature (T-e-method) and via calibrations based on optical emission lines. The source of the discrepancy was investigated in terms of the ionization parameter (U), electron density (N-e), and carbon abundance (C/H). We found a weak correlation between ZR, U, and N-e. However, a moderate correlation was observed between ZR and direct estimates of C/H, suggesting that the previously assumed (C/O)-Z relations in photoionization models used to derive UV carbon-line calibrations may not be valid for AGNs. By combining a large set of abundance estimates for local star-forming regions with those of our AGN sample, we derived a new (C/O)-Z relation. Comparisons between the results of photoionization models that assume this new abundance relation and the UV observational data of our sample produce Z values derived from the C43 index that are consistent with those obtained using the T-e-method. (AU) | |
| FAPESP's process: | 22/07066-6 - Determination of metallicity and chemical abundances in active galactic nuclei (CADA Project) |
| Grantee: | Oli Luiz Dors Junior |
| Support Opportunities: | Regular Research Grants |