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Item Diagnostic diagrams for ram pressure stripped candidates(Royal Astronomical Society) Krabbe, Angela Cristina; Hernandez-Jimenez, José Andrés; Oliveira, Claudia Mendes de; Jaffe, Yara L.; Oliveira Junior, Celso Benedito de; Cardoso, Nathalia Machado; Castelli, Analía V Smith; Dors Junior, Oli Luiz; Cortesi, Arianna; Crossett, Jacob P.This paper presents a method for finding ram pressure stripped (RPS) galaxy candidates by performing a morphological analysis of galaxy images obtained from the Legacy survey. We consider a sample of about 600 galaxies located in different environments such as groups and clusters, tidally interacting pairs and the field. The sample includes 160 RPS previously classified in the literature into classes from J1 to J5, based on the increasing level of disturbances. Our morphological analysis was done using the ASTROMORPHLIB software followed by the inspection of diagnostic diagrams involving combinations of different parameters like the asymmetry (A), concentration (C), Sersic ´ index (n), and bulge strength parameters F(G, M20). We found that some of those diagrams display a distinct region in which galaxies classified as J3, J4, and J5 decouples from isolated galaxies. We call this region as the morphological transition zone and we also found that tidally interacting galaxies in pairs are predominant within this zone. Nevertheless, after visually inspecting the objects in the morphological transition zone to discard obvious contaminants, we ended up with 33 bona fide new RPS candidates in the studied nearby groups and clusters (Hydra, Fornax, and CLoGS sample), of which one-third show clear evidence of unwinding arms. Future works may potentially further increase significantly the samples of known RPS using such method.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 Collaboration