Navegando por Autor "Dors Júnior, Oli Luiz"
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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 – V. The discovery of shocked emission outside the AGN ionization axis(Royal Astronomical Society) Riffel, Rogemar André; Dors Júnior, Oli Luiz; Armah, Mark; Bergmann, Thaisa Storchi; Feltre, Anna; Hägele, Guilhermo Frederico; Cardaci, Mónica Viviana; Dutra, Daniel Ruschel; Krabbe, Angela Cristina; Pérez-Montero, Enrique; Zakamska, Nadia L.; Freitas, Izabel C.We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to > 30000 K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.Item 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 – VII. Direct abundance determination of neon based on optical and infrared emission lines(Royal Astronomical Society) Armah, Mark; Dors Júnior, Oli Luiz; Aydar, Catarina Pasta; Cardaci, Mónica Viviana; Hägele, Guilhermo Frederico; Feltre, Anna; Riffel, Rogério; Riffel, Rogemar André; Krabbe, Angela CristinaFor the first time, neon abundance has been derived in the narrow line region from a sample of Seyfert 2 nuclei. In view of this, we compiled from the literature fluxes of optical and infrared (IR) narrow emission lines for 35 Seyfert 2 nuclei in the local universe (z 0.06). The relative intensities of emission lines were used to derive the ionic and total neon and oxygen abundances through electron temperature estimations (Te-method). For the neon, abundance estimates were obtained by using both Te-method and IR-method. Based on photoionization model results, we found a lower electron temperature [te(Ne iii)] for the gas phase where the Ne2 + is located in comparison with t3 for the O2 + ion. We find that the differences (D) between Ne2 +/H+ ionic abundances calculated from IR-method and Te-method (assuming t3 in the Ne2 +/H+ derivation) are similar to the derivations in star-forming regions (SFs) and they are reduced by a mean factor of ∼3 when te(Ne iii) is considered. We propose a semi-empirical Ionization Correction Factor (ICF) for the neon, based on [Ne II]12.81μm, [Ne III]15.56μm, and oxygen ionic abundance ratios. We find that the average Ne/H abundance for the Seyfert 2s sample is nearly 2 times higher than similar estimate for SFs. Finally, for the very high metallicity regime (i.e. [12 + log(O/H) 8.80]) an increase in Ne/O with O/H is found, which likely indicates secondary stellar production for the neon.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.Item Electron temperature fluctuations in Seyfert galaxies(Royal Astronomical Society) Riffel, Rogemar André; Dors Júnior, Oli Luiz; Krabbe, Angela Cristina; Esteban, CésarWe use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, and Mrk 607) to estimate the electron temperature (Te) fluctuations in the inner 0.4–1.1 kpc region of these galaxies. Based on Te determinations throug the [O III]λ5007/λ4363 emission line ratio of each spaxel, temperature variations are quantified by computing the integrated value of the temperature fluctuation parameter (t 2) projected in the plane of the sky t 2 A, for the first time in active galactic nuclei (AGNs). We find t 2 A values of 0.135, 0.039, and 0.015 for Mrk 79, Mrk 348, and Mrk 607, respectively, which are of the same order or larger than the maximum values reported in star-forming regions and planetary nebulae. Taking into account that t 2 A should be considered a lower limit of the total t 2 in the nebular volume, the results suggest that the impact of such fluctuations on chemical abundance determinations can be important in some AGNs.Item Modeling dark matter halos with nonlinear field theories(APS) Correa, Rafael Augusto Couceiro; Moraes, Henrique Ribeiro da Silva; Dutra, Alvaro de Souza; Dors Júnior, Oli Luiz; Paula, Wayne de; Frederico, TobiasIn the present work, we adopt a nonlinear scalar field theory coupled to the gravity sector to model galactic dark matter. We find analytical solutions for the scalar field considering the weak field gravity limit, which is usually done in galaxy rotation curves analysis and in order to do so we assume an isotropic spacetime and a field potential, with a position dependent form of the superpotential, which entails the nonlinear dynamics of the model with self-interactions. The model introduces a position dependent enhancement of the self-interaction of the scalar fields toward the galaxy center, and while going toward the galaxy border the interaction tends to vanish building a non–self-interacting DM scenario. The developed approach is able to provide a reasonable analytical description of the rotation curves in both dwarf and low surface brightness late-type galaxies, with parameters associated with the dynamics of the scalar field.