Navegando por Autor "Vieira, Lucas Ramos"

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    Ionized gas outflows and shock-heated emission in the highly inclined active galaxy CGCG 012-070
    (Royal Astronomical Society) Vieira, Lucas Ramos; Riffel, Rogemar André; Riffel, Rogério; Dors Junior, Oli Luiz; Bianchin, Marina; Storchi-Bergmann, Thaisa
    Active galactic nuclei (AGNs) exhibit excess mid-infrared H2 emission compared to star-forming galaxies, likely driven by outflows and shocks inferred from integrated spectra. We present optical IFU (integral field unit) observations of the central 2 kpc of the AGN host CGCG 012-070, selected for its pronounced H2 emission excess, to map stellar and gas kinematics. The stellar velocity field is well described by a rotating disc with a line of nodes at 103◦ ± 4◦, with the north-west side approaching and the southeast side receding. Gas kinematics, traced by strong emission lines, show two components: a narrow one (σ 􏰁 200 km s−1 ) in the disc plane following stellar motions, and a broad (σ 􏰂 300 km s−1 ) associated with outflows within the inner ∼1 kpc. Disc gas emission is mainly driven by AGN photoionization, while the outflow also includes shock-heated gas, as indicated by flux ratio diagnostics. The outflows are radiatively driven, with a mass-outflow rate of (0.067 ± 0.026) M⊙ yr−1 and a kinetic coupling efficiency of 0.07 per cent, potentially redistributing gas and contributing to maintenance-mode feedback in CGCG 012-070. Our results provide further evidence that the warm H2 emission excess in nearby AGN is associated with shocks produced by outflows. Observations of other gas phases, such as cold molecular gas, are necessary to gain a more comprehensive understanding of the impact of the outflows on the host galaxy.
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    Metallicity of active galactic nuclei from ultraviolet and optical emission lines - II. Revisiting the C43 metallicity calibration and its implications
    (Oxford) Dors Junior, Oli Luiz; Oliveira, Celso Benedito de; Cardaci, Mónica Viviana; Hägele, Guillermo Federico; Armah, Mark; Riffel, Rogemar André; Vieira, Lucas Ramos; Almeida, Gleicy Caroline de; Morais, Istenio Nunes de; Santos, Pedro Camargo
    In this study, a new semi-empirical calibration is proposed between ultraviolet emission lines (CIII]λ1909, CIVλ1549, HeII]λ1640) of type 2 active galactic nuclei (AGNs) and their metallicity (Z). This calibration is derived by comparing a large sample of 106 objects (data taken from the literature) located over a wide range of redshifts (0 􏰁 z 􏰁 4.0) with predictions from photoionization models that adopt a recent C/O–O/H relation derived via estimates using the Te method, which is considered the most reliable method. We found that the new calibration produces Z values in agreement (within an uncertainty of ±0.1 dex) with those from other calibrations and from estimates via the Te-method. We find also that AGN metallicities are already high at early epochs, with no evidence for monotonic evolution across the redshift range 0 􏰁 z 􏰁 12. Notably, the highest metallicities in our sample, reaching up to 4 Z⊙, are found in objects at 2 􏰁 z 􏰁 3. This redshift range coincides with the peak of the cosmic star formation rate history, suggesting a strong connection between the major epoch of star formation, black hole growth, and rapid metal enrichment in the host galaxies of AGNs. Furthermore, our analysis reveals no significant correlation between AGN metallicity and radio properties (radio spectral index or radio luminosity) or host galaxy stellar mass. The lack of a clear mass–metallicity relation, consistent with findings for local AGNs, suggests that the chemical evolution of the nuclear gas is decoupled from the global properties of the host galaxy.