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Item Oxygen abundances in the narrow line regions of Seyfert galaxies and the metallicity–luminosity relation(Royal Astronomical Society) Armah, Mark; Riffel, Rogério; Dors Junior, Oli Luiz; Oh, Kyuseok; Koss, Michael J.; Ricci, Claudio; Trakhtenbrot, Benny; Valerdi, Mabel; Riffel, Rogemar André; Krabbe, Angela CristinaWe present oxygen abundances relative to hydrogen (O/H) in the narrow line regions (NLRs) gas phases of Seyferts 1 (Sy 1s) and Seyferts 2 (Sy 2s) active galactic nuclei (AGNs). We used fluxes of the optical narrow emission line intensities [Å] of 561 Seyfert nuclei in the local Universe ( z ≲ 0.31) from the second catalogue and data release (DR2) of the BAT AGN Spectroscopic Survey, which focuses on the Swift-BAT hard X-ray (≳ 10 keV) detected AGNs. We derived O/H from relative intensities of the emission lines via the strong-line methods. We find that the AGN O/H abundances are related to their hosts stellar masses and that they follow a downward redshift evolution. The derived O/H together with the hard X-ray luminosity (LX) were used to study the X-ray luminosity–metallicity (LX–ZNLR) relation for the first time in Seyfert galaxies. In contrast to the broad-line focused (LX–ZBLR) studies, we find that the LX–ZNLR exhibit significant anticorrelations with the Eddington ratio (λEdd) and these correlations vary with redshifts. This result indicates that the low-luminous AGNs are more actively undergoing interstellar medium enrichment through star formation in comparison with the more luminous X-ray sources. Our results suggest that the AGN is somehow driving the galaxy chemical enrichment, as a result of the inflow of pristine gas that is diluting the metal rich gas, together with a recent cessation on the circumnuclear star-formation.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 Gas-phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA: evidence of metal-poor accretion(Royal Astronomical Society) Nascimento, Janaína Correa do; Dors Junior, Oli Luiz; Bergmann, Thaisa Storchi; Mallmann, Nícolas Dullius; Riffel, Rogério; Ilha, Gabriele da Silva; Riffel, Rogemar André; Rembold, Sandro Barboza; Deconto-Machado, Alice; Costa, Luiz N. da; Armah, MarkWe derive the metallicity (traced by the O/H abundance) of the narrow-line region (NLR) of 108 Seyfert galaxies as well as radial metallicity gradients along their galaxy discs and of these of a matched control sample of no active galaxies. In view of that, observational data from the SDSS-IV MaNGA survey and strong emission-line calibrations taken from the literature were considered. The metallicity obtained for the NLRs was compared to the value derived from the extrapolation of the radial oxygen abundance gradient, obtained from H II region estimates along the galaxy disc, to the central part of the host galaxies. We find that, for most of the objects (∼ 80 per cent), the NLR metallicity is lower than the extrapolated value, with the average difference (D ) between these estimates ranging from 0.16 to 0.30 dex. We suggest that D is due to the accretion of metal-poor gas to the AGN that feeds the nuclear supermassive black hole (SMBH), which is drawn from a reservoir molecular and/or neutral hydrogen around the SMBH. Additionally, we look for correlations between D and the electron density (Ne), [O III]λ5007, and H α luminosities, extinction coefficient (AV) of the NLRs, as well as the stellar mass (M∗) of the host galaxies. Evidence of an inverse correlation between the D and the parameters Ne, M∗, and Av was found.Item Cosmic metallicity evolution of Active Galactic Nuclei: implications for optical diagnostic diagrams(Royal Astronomical Society) Dors Junior, Oli Luiz; Cardaci, Mónica Viviana; Hägele, Guilhermo Frederico; Ilha, Gabriele da Silva; Oliveira Junior, Celso Benedito de; Riffel, Rogemar André; Riffel, Rogério; Krabbe, Angela CristinaWe analyse the validity of optical diagnostic diagrams relying on emission-lines ratios and in the context of classifying Active Galactic Nuclei (AGNs) according to the cosmic metallicity evolution in the redshift range. In this regard, we fit the results of chemical evolution models (CEMs) to the radial gradients of the N/O abundances ratio derived through direct estimates of electron temperatures (Te-method) in a sample of four local spiral galaxies. This approach allows us to select representative CEMs and extrapolate the radial gradients to the nuclear regions of the galaxies in our sample, inferring in this way the central N/O and O/H abundances. The nuclear abundance predictions for theoretical galaxies from the selected CEMs, at distinct evolutionary stages, are used as input parameters in AGN photoionization models built with the Cloudy code. We found that standard BPT diagnostic diagrams are able to classify AGNs with oxygen abundances at redshift. On the other hand, the He iiλ4685/Hβ versus [N ii]λ6584/Hα diagram produces a reliable AGN classification independent of the evolutionary stage of these objects.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.