Navegando por Autor "Bergmann, Thaisa Storchi"
Agora exibindo 1 - 4 de 4
Resultados por página
Opções de Ordenação
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 – X. Sulphur abundance estimates(Royal Astronomical Society) Dors Junior, Oli Luiz; Valerdi, Mabel; Riffel, Rogemar André; Riffel, Rogério; Cardaci, Mónica Viviana; Hägele, Guilhermo Frederico; Armah, Mark; Revalski, Mitchell; Flury, Sophia; Lemes, Priscila Freitas; Amôres, Eduardo; Krabbe, Angela Cristina; Binette, Luc; Feltre, Anna; Bergmann, Thaisa StorchiFor the first time, the sulphur abundance relative to hydrogen (S/H) in the narrow-line regions of a sample of Seyfert 2 nuclei (Sy 2s) has been derived via direct estimation of the electron temperature. Narrow emission-line intensities from the Sloan Digital Sky Survey (SDSS) Data Release 17 (DR17) [in the wavelength range 3000 < λ(Å) < 9100] and from the literature for a sample of 45 nearby (z < 0.08) Sy 2s were considered. Our direct estimates indicate that Sy 2s have similar temperatures in the gas region where most of the S+ ions are located in comparison with that of star-forming regions (SFs). However, Sy 2s present higher temperature values (∼10 000 K) in the region where most of the S2+ ions are located relative to that of SFs. We derive the total sulphur abundance in the range of 6.2 12 + log(S/H) 7.5, corresponding to 0.1–1.8 times the solar value. These sulphur abundance values are lower by ∼0.4 dex than those derived in SFs with similar metallicity, indicating a distinct chemical enrichment of the interstellar medium (ISM) for these object classes. The sulphur abundance relative to oxygen (S/O) values for our Sy 2 sample present an abrupt (∼0.5 dex) decrease with increasing oxygen abundance relative to hydrogen (O/H) for the high-metallicity regime [12 + log(O/H) 8.7)], what is not seen for the SFs. However, when our Sy 2 estimates are combined with those from a large sample of SFs, we did not find any dependence between S/O and O/H.Item 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 N2, um indicador de metalicidade para AGN(2020-10-15) Carvalho, Sarita Pereira de; Dors Junior, Oli Luiz; Oliveira Filho, Irapuan Rodrigues de; Bergmann, Thaisa Storchi; Riffel, Rogemar André; Krabbe, Angela Cristina; São José dos CamposNeste trabalho apresentamos uma calibração semi-empírica entre a metalicidade (Z) de Núcleos Ativos de Galáxias tipo Seyfert 2 e a razão de intensidade de linhas de emissão N2=log([N II] lambda6584/H alpha). Esta calibração foi derivada utilizando um diagrama [O III] lambda 5007/[O II] lambda3727 versus N2 contendo dados observacionais e resultados de modelos de fotoionização construídos com o código Cloudy. A amostra observacional consiste em 463 núcleos Seyfert 2 (redshift z ? 0.4) obtidos do banco de dados do Sloan Digital Sky Survey DR7. A relação obtida Z-N 2 é válida para o intervalo 0.3 ? (Z/Z?) ? 2.0 a qual corresponde -0.7 ? (N 2) ? 0.6. Os efeitos da variação do parâmetro de ionização (U), densidade eletrônica e a inclinação da distribuição espectral de energia nas estimativas de Z são da ordem da incerteza produzida pelo erro observacional de N2. Este resultado indica a grande confiabilidade de nossa calibração Z -N 2. Obtivemos uma relação entre U e a razão de linhas [O III]/[O II], quase independente de outro parâmetro nebular.