Dors Junior, Oli LuizOliveira Junior, Celso Benedito deCardaci, Mónica VivianaHagele, Guillermo FedericoMorais, Istenio Nunes deJi, XihanRiffel, Rogemar AndréRiffel, RogérioMezcua, MarAlmeida, Gleicy Caroline deSantos, Pedro CamargoMellos, Maitê Silvana de Zorzi de2025-08-182025-08-18https://repositorio.univap.br/handle/123456789/1025Metallicity (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 < λ(Å) < 2000] and optical [3000 < λ(Å) < 7000] emission-line measurements for a sample of 11 AGNs (nine at z < 0.4 and two at z ∼ 2.4). Metallicity values for our sample were derived using a semi-empirical calibration based on the C43 = log[(C IVλ1549 + C III]λ1909)/He IIλ1640] emission-line ratio and compared with those obtained via direct measurement of the electron temperature (Te-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 (Ne), and carbon abundance (C/H). We found a weak correlation between ZR, U, and Ne. 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 Te-method.PDFen-USArtigos de PeriódicosMonthly Notices of the Royal Astronomical Society10.1093/mnras/staf727GalaxiesDORS JUNIOR, Oli Luiz et al. Metallicity of active galactic nuclei from ultraviolet and optical emission lines: I. Carbon abundance dependence. Monthly Notices of the Royal Astronomical Society, v. 540, n. 2, p. 1608-1625, 2025. Disponível em: 10.1093/mnras/staf727.Universidade do Vale do ParaíbaUniversidad Nacional de La PlataUniversity of CambridgeUniversidade Federal de Santa MariaUniversidade Federal do Rio Grande do SulInstitute of Space SciencesInstitut d’Estudis Espacials de Catalunya