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Item Chemical abundance of LINER galaxies – metallicity calibrations based on SDSS-IV MaNGA(Royal Astronomical Society) Oliveira Junior, Celso Benedito de; Krabbe, Angela Cristina; Hernandez-Jimenez, Jose Andres; Dors Junior, Oli Luiz; Zinchenko, Igor; Hägele, Guilhermo Frederico; Cardaci, Mónica Viviana; Monteiro, Adriano FranciscoThe ionizing source of low-ionization nuclear emission-line regions (LINERs) is uncertain. Because of this, an empirical relation to determine the chemical abundances of these objects has not been proposed. In this work, for the first time, we derived two semi-empirical calibrations based on photoionization models to estimate the oxygen abundance of LINERS as a function of the N2 and O3N2 emission-line intensity ratios. These relations were calibrated using oxygen abundance estimations obtained by comparing the observational emission-line ratios of 43 LINER galaxies (taken from the MaNGA survey) and grids of photoionization models built with the cloudy code assuming post-asymptotic giant branch stars with different temperatures. We found that the oxygen abundance of LINERs in our sample is in the range, with a mean value of . We recommend the use of the N2 index to estimate the oxygen abundances of LINERs, since the calibration with this index presented a much smaller dispersion than the O3N2 index. In addition, the estimated metallicities are in good agreement with those derived by extrapolating the disc oxygen abundance gradients to the centre of the galaxies showing that the assumptions of the models are suitable for LINERs. We also obtained a calibration between the logarithm of the ionization parameter and the [O iii]/[O ii] emission-line ratio.Item Chemical abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA(Royal Astronomical Society) Krabbe, Angela Cristina; Oliveira Junior, Celso Benedito de; Zinchenko, Igor A.; Hernández-Jiménez, Jose Andres; Dors Júnior, Oli Luiz; Hägele, Guilhermo Frederico; Cardaci, Mónica Viviana; Telles, Nayra ReginaChemical abundance determinations in Low-Ionization Nuclear Emission-line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC 4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disc abundance gradient, on calibrations between O/H abundance and strong emission-lines for active galactic nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-asymptotic giant branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN, and p-AGB photoionization models produce similar O/H values for the UGC 4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC 4805 nucleus probably has a stellar origin rather than an AGN.Item Chemical abundances in Seyfert galaxies – IX. Helium abundance estimates(Royal Astronomical Society) Dors Junior, Oli Luiz; Valerdi, Mabel; Lemes, Priscila Freitas; Krabbe, Angela Cristina; Riffel, Rogemar André; Amôres, Eduardo Brescansin; Riffel, Rogério; Armah, Mark; Monteiro, Adriano Francisco; Oliveira Junior, Celso Benedito deFor the first time, the helium abundance relative to hydrogen (He/H), which relied on direct measurements of the electron temperature, has been derived in the narrow line regions (NLRs) from a local sample of Seyfert 2 nuclei. In view of this, optical emission line intensities [3000 < λ(Å) < 7000] of 65 local Seyfert 2 nuclei (z < 0.2), taken from Sloan Digital Sky Survey Data Release 15 and additional compilation from the literature, were considered. We used photoionization model grid to derive an Ionization Correction Factor (ICF) for the neutral helium. The application of this ICF indicates that the NLRs of Seyfert 2 present a neutral helium fraction of ∼50 per cent in relation to the total helium abundance. We find that Seyfert 2 nuclei present helium abundance ranging from 0.60 to 2.50 times the solar value, while ∼85 per cent of the sample present oversolar abundance values. The derived (He/H)–(O/H) abundance relation from the Seyfert 2 is stepper than that of star-forming regions (SFs) and this difference could be due to excess of helium injected into the interstellar medium by the winds of Wolf–Rayet stars. From a regression to zero metallicity, by using Seyfert 2 estimates combined with SFs estimates, we obtained a primordial helium mass fraction Yp = 0.2441 ± 0.0037, a value in good agreement with the one inferred from the temperature fluctuations of the cosmic microwave background by the Planck CollaborationItem Chemical abundances in Seyfert galaxies – VI. Empirical abundance calibration(Royal Astronomical Society) Dors Júnior, Oli LuizWe derived a bi-dimensional calibration between the emission-line ratios R23 =([OII]λ3726+λ3729+[OIII]λ4959+ λ5007)/H β , P = [([O III] λ4959 + λ5007)/H β ]/R23 and the oxygen abundance relative to hydrogen (O/H) in the gas phase of Seyfert 1 and 2 nuclei. In view of this, emission-line intensity ratios for a sample of objects taken from the Sloan Digital Sky Survey Data Release 7 measured by the MPA/JHU group and direct estimates of O/H based on Te-method, adapted for active galactic nuclei (AGNs), are considered. We find no variation of R23 observed along the radii of AGNs, which shows that this line ratio is a good oxygen abundance (O/H) indicator for the class of objects considered in this work. The derived O/H = f(R23, P) relation produces O/H values similar to estimations via Te-method in a wide range of metallicities [8.0 < 12 + log (O/H) < 9.2]. Conversely to star-forming regions in the high-metallicity regime, R23 shows a positive correlation trend with O/H in AGNs. This indicates that the hardness of ionizing radiation is not affected by the metallicities in these objects or narrow-line regions are not significantly modified by changes in the spectral energy distribution due to metallicity variations.Item Chemical abundances in Seyfert galaxies – VIII. Argon abundance estimates(Royal Astronomical Society) Monteiro, Adriano Francisco; Dors Júnior, Oli LuizFor the first time, the argon abundance relative to hydrogen abundance (Ar/H) in the narrow line region of a sample of Seyfert 2 nuclei has been derived. In view of this, optical narrow emission line intensities of a sample of 64 local Seyfert 2 nuclei (z < 0.25) taken from Sloan Digital Sky Survey DR7 and measured by the MPA/JHU group were considered. We adopted the Te-method for AGNs, which is based on direct determination of the electron temperature, together with a grid of photoionization model results, built with the CLOUDY code, to obtain a method for the derivation of the Ar/H abundance. We find that for a metallicity range of 0.2 (Z/Z) 2.0, Seyfert 2 nuclei present Ar/H abundance ranging from ∼0.1 to ∼3 times the argon solar value, adopting log(O/H) = −3.31 and log(Ar/H) = −5.60. These range of values correspond to 8.0 (12 + log(O/H) 9.0 and 5.4 (12 + log(Ar/H) 6.9, respectively. The range of Ar/H and Ar/O abundance values obtained from our sample are in consonance with estimations from extrapolations of the radial abundance gradients to the central parts of the disc for four spiral galaxies. We combined our abundance results with estimates obtained from a sample of H II galaxies, which were taken from the literature, and found that the Ar/O abundance ratio decreases slightly as the O/H abundance increases.