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We 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 [$3\,500, Comment: 17 pages, 12 figures, Accepted for publication in MNRAS, doi: 10.1093/mnras/stad217

We derived a bi-dimensional calibration between the emission-line ratios $R_{23}= ([\mathrm{ O}\, {\small {\rm II}}]\,\lambda 3726 +\lambda 3729 +[\mathrm{ O}\mathrm{ }\, {\small {\rm III}}]\,\lambda 4959 + \lambda 5007)/\rm H\,\beta$, ${\it P}=[([\mathrm{ O}\, {\small {\rm III}}]\,\lambda 4959+\lambda 5007)/{\rm H}\,\beta ]/R_{23}$ 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 [$\rm 8.0 \: \lesssim \: 12+\log \,(O/H) \: \lesssim \: 9.2$]. 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.

We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk79, Mrk348 and Mrk607) to estimate the electron temperature ($T_{\rm e}$) fluctuations in the inner 0.4-1.1 kpc region of these galaxies. Based on $T_{\rm e}$ determinations through the [O III]$\lambda5007$/$\lambda4363$ emission line ratio of each spaxel, temperature variations are quantified by computing the integrated value of the temperature fluctuation parameter ($t^{\rm 2}$) projected in the plane of the sky $t_{\rm A}^{\rm 2}$, for the first time in Active Galactic Nuclei. We find $t_{\rm A}^{\rm 2}$ values of 0.135, 0.039, and 0.015 for Mrk79, Mrk348, and Mrk607, 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 $t_{\rm A}^{\rm 2}$ 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., Comment: Accepted for publication in MNRAS Letters

For 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 [$3000 \: < λ\: < \: 7000$] 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 $\sim$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 $\sim$85 per cent of the sample present over-solar 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 $Y_{\rm p}$=0.2441$\pm$0.0037, a value in good agreement with the one inferred from the temperature fluctuations of the cosmic microwave background by the Planck Collaboration, i.e. $Y_{\rm p}$=0.2471$\pm$0.0003, 23 pages, 12 figures, 3 tables, accepted for publication in MNRAS

The ionizing source of Low Ionization Nuclear Emission 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 {\sc Cloudy} code assuming post-Asymptotic Giant Branch (post-AGB) stars with different temperatures. We found that the oxygen abundance of LINERs in our sample is in the $\rm 8.48, 16 pages, 14 figures, 3 tables, accepted for publication in MNRAS

For 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/Zsolar) < 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 disk for four spiral galaxies. We combined our abundance results with estimates obtained from a sample of Hii galaxies, which were taken from the literature, and found that the Ar/O abundance ratio decreases slightly as the O/H abundance increases., Accepted for publication by MNRAS

In this study we define a new sample of distant powerful radio galaxies in order to study their host-galaxy properties and provide targets for future observations of HI absorption with new radio telescopes and to understand the fuelling and feedback from such sources. We have cross-matched the Sydney University Molonglo Sky Survey (SUMSS) radio catalogue at 843 MHz with the VISTA Hemisphere Survey (VHS) near-infrared catalogue using the Likelihood Ratio technique. Photometric redshifts from the Dark Energy Survey are then used to assign redshifts to the radio source counterparts. We found a total of 249 radio sources with photometric redshifts over a 148 deg^2 region. By fitting the optical and near-infrared photometry with spectral synthesis models we determine the stellar mass and star-formation rates of the radio sources, finding typical stellar masses of 10^{11} - 10^{12}M$_{\odot}$ for the powerful high-redshift radio galaxies. We also find a population of low-mass blue galaxies. However, by comparing the derived star-formation rates to the radio luminosity, we suggest that these sources are false positives in our likelihood ratio analysis. Follow up, higher-resolution (, 11 pages, 9 figures. Accepted for publication in MNRAS

Chemical abundance determinations in Low-Ionization Nuclear 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 UGC4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC4805 nucleus based on the extrapolation of the disk 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 UGC4805 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 UGC4805 nucleus probably has a stellar origin rather than an AGN., 17 pages, 13 figures

Nuclear Activity in Galaxies Across Cosmic Time, Proceedings of the conference held 7-11 October 2019 in Addis Ababa, Ethiopia. Edited by Mirjana Pović et al. Proceedings of the International Astronomical Union, Volume 356, pp. 61-65, We present a new tool for the analysis of the optical emission lines of the gas in the Narrow Line Region (NLR) around Active Galactic Nuclei (AGNs). This new tool can be used in large samples of objects in a consistent way using different sets of optical emission-lines taking into the account possible variations from the O/H - N/O relation. The code compares certain observed emission-line ratios with the predictions from a large grid of photoionization models calculated under the most usual conditions in the NLR of AGNs to calculate the total oxygen abundance, nitrogen-to-oxygen ratio and ionization parameter. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes from the literature. Our results confirm the high metallicity of the objects of the sample and provide consistent values with the direct method. The usage of models to calculate precise ICFs is mandatory when only optical emission lines are available to derive chemical abundances using the direct method in NLRs of AGN., Financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

The Southern Photometric Local Universe Survey (S-PLUS) is a novel project that aims to map the Southern Hemisphere using a twelve filter system, comprising five broad-band SDSS-like filters and seven narrow-band filters optimized for important stellar features in the local universe. In this paper we use the photometry and morphological information from the first S-PLUS data release (S-PLUS DR1) cross-matched to unWISE data and spectroscopic redshifts from Sloan Digital Sky Survey DR15. We explore three different machine learning methods (Gaussian Processes with GPz and two Deep Learning models made with TensorFlow) and compare them with the currently used template-fitting method in the S-PLUS DR1 to address whether machine learning methods can take advantage of the twelve filter system for photometric redshift prediction. Using tests for accuracy for both single-point estimates such as the calculation of the scatter, bias, and outlier fraction, and probability distribution functions (PDFs) such as the Probability Integral Transform (PIT), the Continuous Ranked Probability Score (CRPS) and the Odds distribution, we conclude that a deep-learning method using a combination of a Bayesian Neural Network and a Mixture Density Network offers the most accurate photometric redshifts for the current test sample. It achieves single-point photometric redshifts with scatter (σNMAD) of 0.023, normalized bias of -0.001, and outlier fraction of 0.64% for galaxies with r_auto magnitudes between 16 and 21. © 2021 Elsevier B.V. All rights reserved., The author acknowledges the financial support given by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES, grant 88887.470064/2019-00) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grant 169181/2017-0), during the development of this research. L. S. J. acknowledges support from Brazilian agencies FAPESP (2019/10923-5) and CNPq (304819/2017-4). L. N. acknowledges the financial support provided by the São Paulo Research Foundation (FAPESP), Brazil (grant 2019/01312-2 and 2014/10566-4). M. L. B. acknowledges the financial support provided by the São Paulo Research Foundation (FAPESP), Brazil (grant 2018/09165-6 and 2019/23388-0). C. Q. acknowledges the financial support provided by the São Paulo Research Foundation, Brazil (grant 2015/11442-0 and 2019/06766-1) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil. F. R. H. thanks FAPESP for the financial support through the program 2018/21661-9. J. L. N. C. is grateful for the financial support received from the Southern Office of Aerospace Research and development (SOARD), grants FA9550-18-1-0018 and FA9550-22-1-0037, of the Air Force Office of the Scientific Research International Office of the United States (AFOSR/IO). M. L. L. D. acknowledges the polish NCN, Poland grant number 2019/34/E/ST9/00133. S. A. acknowledges support under the grant 5077 financed by IAASARS/NOA. Y. J-T has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 898633. Y. J-T. also acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

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 ≳30000K. 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. © 2020 The Author(s)., This study was financed in part by CNPq, FAPERGS, and FAPESP. AF acknowledges the support from grant PRIN MIUR2017-20173ML3WW−001. EPM acknowledges financial support from the project ‘Estallidos6’ AYA2016-79724-C4. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NationalScience Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We compare the oxygen abundance (O/H) of the narrow-line regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass-metallicity relation of active galactic nuclei (AGNs) at low redshifts (z, We thank the referee for helping to improve this paper with her/his constructive feedback. OLD and ACK thank FAPESP and CNPq for the financial support. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute forAstronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. We also thank to Max-Planck-Institute forAstrophysics and John Hopkins University for Physical properties for galaxies andAGNs in the SDSS: Data catalogues from SDSS studies atMPA/JHU. This research hasmade use of the VizieR catalogue access tool, CDS, Strasbourg, France (doi: 10.26093/cds/vizier). The original description of the VizieR service was published in AAS, 143, 23. This work has also made use of the computing facilities of the Laboratory of Astroinformatics (IAG/USP, NAT/Unicsul), whose purchase was made possible by the Brazilian agency FAPESP (grant no. 2009/54006-4) and the INCT-A.

We build detailed composite models of photoionization and shock ionization based on the suma code to reproduce emission lines emitted from the Narrow Line Regions (NLR) of Seyfert 2 nuclei. The aim of this work is to investigate diagram active galactic nucleus (AGN) positions according to shock parameters, shock effects on the gas temperature and ionization structures and derive a semi-empirical abundance calibration based on emission-line ratios little sensitive to the shock presence. The models were used to reproduce optical (3000 < λ(Å) < 7000) emission line intensities of 244 local ($z \: \lesssim \: 0.4$) Seyfert 2s, whose observational data were selected from Sloan Digital Sky Survey DR7. Our models suggest that shocks in Seyfert 2 nuclei have velocities in the range of 50-300 $\rm km \: s^{-1}$ and imply a narrower metallicity range ($0.6 \: \lesssim \: (Z/Z_{\odot }) \: \lesssim \: 1.6$) than those derived using pure photoionization models. Our results indicate that shock velocity in AGNs cannot be estimated using standard optical line ratio diagrams, based on integrated spectra. Our models predict a different temperature structure and $\rm O^{+}$/O and $\rm O^{2+}$/O fractional abundances throughout the NLR clouds than those derived from pure photoionization models, mainly in shock-dominated objects. This suggests that, in order to minimize the shock effects, the combination of emission-lines emitted by ions with similar intermediate ionization potential could be good metallicity indicators. Finally, we derive two calibrations between the N/O abundance ratio and the N2O2 = log([N ii]λ6584/[O ii]λ3727) and N2 = log([N ii]λ6584/H α) indexes which agree with that derived from pure photoionization models. © 2020 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society, We are grateful to the referee for his/her dedicated work in reviewing our paper. OLD and ACK are grateful to Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Cient ' ifico e Tecnologico (CNPq). RAR thanks partial financial support from Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (17/2551-0001144-9 and 16/25510000251-7) and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (302280/2019-7). MVC and GFH are grateful to Consejo Nacional de Investigaciones Cient ' ificas y T ' ecnicas (CONICET)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic nuclei and the N2 = log([N HP.6584/11 cy) emission-line intensity ratio. This calibration was derived through the [0 m]..5007/[0 u[),3727 versus N2 diagram containing observational data and photoionization model results obtained with the CLOUDY code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift z < 0.4) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z N2 relation is valid for the range 0.3 r< ( Z/Zo) 2.0 that corresponds to 0.7 < (N2) < 0.6. The effects of varying the ionization parameter (U), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z N2 calibration. A relation between U and the IOutj/[OIII line ratio, almost independent of other nebular parameter, was obtained., This work is partially supported by the Brazilian agencies FAPESP, CAPES, and CNPq. EPM acknowledges support from the Spanish MINECO project Estallidos 6 AYA2016-79724-C4 and by the Spanish Science Ministry Centro de Excelencia Severo Ochoa Program under grant no. SEV-2017-0709.

Made available in DSpace on 2021-06-25T12:17:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-14 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In 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. DCTA, Inst Tecnol Aeronaut, BR-12228900 Sao Jose Dos Campos, SP, Brazil Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo, Brazil Univ Estadual Paulista, Campus Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil Univ Vale Paraiba, BR-12244000 Sao Jose Dos Campos, SP, Brazil Univ Estadual Paulista, Campus Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil CAPES: 88887.310593/2018-00-ITA FAPESP: 2016/03276-5 FAPESP: 2017/26646-5

We investigate the discrepancy between oxygen abundance estimations for narrow-line regions of active galactic nuclei (AGNs) type Seyfert 2 derived using direct estimations of the electron temperature (T-e-method) and those derived using photoionization models. In view of this, observational emission-line ratios in the optical range (3000 < lambda(angstrom) < 7000) of Seyfert 2 nuclei compiled from the literature were reproduced by detailed photoionization models built with the CLOUDY code. We find that the derived discrepancies are mainly due to the inappropriate use of the relations between temperatures of the low (t(2)) and high (t(3)) ionization gas zones derived for H II regions in AGN chemical abundance studies. Using a photoionization model grid, we derived a new expression for t(2) as a function of t(3) valid for Seyfert 2 nuclei. The use of this new expression in the AGN estimation of the O/H abundances based on Te-method produces O/H abundances slightly lower (about 0.2 dex) than those derived from detailed photoionization models. We also find that the new formalism for the T-e-method reduces by about 0.4 dex the O/H discrepancies between the abundances obtained from strong emission-line calibrations and those derived from direct estimations. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, OLD and ACK are grateful to Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ). MA is grateful to Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES). MVC and GFH are grateful to CONICET. OLD thanks the kindly hospitality of the Kavli Institute for Cosmology staff where part of thisworkwas developed. RMacknowledges ERC Advanced Grant 695671 'QUENCH` and support by the Science and Technology Facilities Council (STFC).

We present an observational study of the impacts of the interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 {\AA} obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for fifteen galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code STARLIGHT. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by the young/intermediate stellar populations. This result differs from the one derived for isolated galaxies where the old stellar population dominates the disc surface brightness. We interpreted such different behavior as being due to the effect of gas inflows along the disk of interacting galaxies on the star formation in a time scale of the order of about 2Gyr. We also found that, in general, the secondary galaxy of the pairs has a higher contribution of the young stellar population than the primary one. We compared the estimated values of the stellar and nebular extinctions derived from the synthesis method and the H{\alpha}/H\b{eta} emission-line ratio finding that the nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. We neither found a correlation between stellar metallicities and ages while a positive correlation between nebular metallicities and stellar ages was obtained, with the older regions being the most metal-rich., Comment: Accepted for publication in MNRAS

The Southern Photometric Local Universe Survey (S-PLUS) is imaging similar to 9300 deg(2) of the celestial sphere in 12 optical bands using a dedicated 0.8mrobotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k x 9.2k e2v detector with 10 mu m pixels, resulting in a field of view of 2 deg(2) with a plate scale of 0.55 arcsec pixel-1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (vertical bar b vertical bar > 30 degrees, 8000 deg(2)) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg(2)). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/[OII], Ca H + K, Hd, G band, Mg b triplet, H alpha, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (dz /(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z < 0.4, thus producing a 3D map of the local Universe over a volume of more than 1 (Gpc/h)(3). The final S-PLUS catalogue will also enable the study of star formation and stellar populations in and around the Milky Way and nearby galaxies, as well as searches for quasars, variable sources, and low-metallicity stars. In this paper we introduce the main characteristics of the survey, illustrated with science verification data highlighting the unique capabilities of S-PLUS. We also present the first public data release of similar to 336 deg(2) of the Stripe 82 area, in 12 bands, to a limiting magnitude of r = 21, available at datalab.noao.edu/splus.© 2019 The Author(s).Published by Oxford University Press on behalf of the Royal Astronomical Society, The S-PLUS project, including the T80S robotic telescope and the S-PLUS scientific survey, was founded as a partnership between the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), the Observatorio Nacional (ON), the Federal University of Sergipe (UFS), and the Federal University of Santa Catarina (UFSC), with important financial and practical contributions from other collaborating institutes in Brazil, Chile (Universidad de La Serena), and Spain (Centro de Estudios de Fisica del Cosmos de Aragon, CEFCA). The members of the collaboration are grateful for the support received from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq; grants 312333/2014-5, 306968/2014-2, 142436/2014-3, 459553/2014-3, 400738/2014-7, 302037/2015-2, 312307/2015-2, 300336/2016-0, 304184/2016-0, 304971/2016-2, 401669/2016-5, 308968/2016-6, 309456/2016-9, 421687/2016-9, 150237/2017-0, 311331/2017-3, 304819/2017-4, and 200289/2017-9), FAPESP (grants 2009/54202-8, 2011/51680-6, 2014/07684-5, 2014/11806-9, 2014/13723-3, 2014/18632-6, 2016/17119-9, 2016/12331-0, 2016/21532-9, 2016/21664-2, 2016/23567-4, 2017/01461-2, 2017/23766-0, 2018/02444-7, and 2018/21661-9), the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES; grants 88881.030413/2013-01 and 88881.156185/2017-01), the Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ; grants 202.876/2015, 202.835/2016, and 203.186/2016), the Financiadora de Estudos e Projetos (FINEP; grants 1217/13-01.13.0279.00 and 0859/10-01.10.0663.00), the Direccion de Investigacion y Desarrollo de la Universidad de La Serena (DIDULS/ULS; projects PR16143 and PTE16146 and the Programa de Investigadores Asociados), and the Direccion de Postgrado y Postitulo. TCB, VMP, and DDW acknowledge the support from the Physics Frontier Center for the Evolution of the Elements (JINA-CEE) through the US National Science Foundation (grant PHY 14-30152). JLNC is grateful for financial support received from the Southern Office of Aerospace Research and development (SOARD; grants FA9550-15-1-0167 and FA9550-18-1-0018) of the Air Force Office of the Scientific Research International Office of the United States (AFOSR/IO). YJT and RAD acknowledge support from the Spanish National Research Council (CSIC) I-COOP + 2016 program (grant COOPB20263), and the Spanish Ministry of Economy, Industry, and Competitiveness (MINECO; grants AYA2013-48623-C2-1-P and AYA2016-81065-C2-1-P). RAOM acknowledges support from the Direccion General de Asuntos del Personal Academico of the Universidad Nacional Autonoma de Mexico (DGAPA-UNAM) through a post-doctoral fellowship from the Programa de Becas Posdoctorales en la UNAM. This work has made use of data from the Sloan Digital Sky Survey. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Enenergy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/.The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), the New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. This publication makes use of data products from the Widefield Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. We are grateful for the contributions of CTIO staff in helping in the construction, commissioning, and maintenance of the telescope and camera and we are particularly thankful to the CTIO director, Steve Heathcote, for his support at every phase, without which this project would not have been completed. We thank Cesar Iniguez for making the 2D measurements of the filter transmissions at CEFCA. We warmly thank David Cristobal-Hornillos and his group for helping us to install and run the reduction package JYPE version 0.9.9 in the S-PLUS computer system in Chile. We warmly thank Mariano Moles, Javier Cenarro, Tamara Civera, Sergio Chueca, Javier Hernandez Fuertes, Antonio Marin Franch, Jesus Varella, and Hector Vazquez Ramio -the success of the S-PLUS project relies on the dedication of these and other CEFCA staff members in building OAJ and running J-PLUS and J-PAS. We deeply thank Rene Laporte and INPE, as well as Keith Taylor, for their contributions to the T80S camera.

We present a new methodology for the analysis of the emission lines of the interstellar medium in the narrow-line regions around type-2 active galactic nuclei. Our aim is to provide a recipe that can be used for large samples of objects in a consistent way using different sets of optical emission lines that takes into the account possible variations from the O/H-N/O relation to use [N II] lines. Our approach consists of a bayesian-like comparison between certain observed emission-line ratios sensitive to total oxygen abundance, nitrogen-to-oxygen ratio, and ionization parameter with the predictions from a large grid of photoionization models calculated under the most usual conditions in this environment. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes and determinations of their chemical properties from detailed models in the literature. Our results agree within the errors with other results and confirm the high metallicity of the objects of the sample, with N/O values consistent with a large secondary production of N, but with a large dispersion. The obtained ionization parameters for this sample are much larger than those for star-forming object at the same metallicity. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, This work has been partly funded by the Spanish MINECO project Estallidos 6 AYA2016-79724-C4 and the Junta de Andalucía for grant EXC/2011 FQM-7058. This work has been also supported by the Spanish Science Ministry ’Centro de Excelencia Severo Ochoa Program under grant SEV-2017-0709. EPM also acknowledges support from the CSIC intramural grant 20165010-12 and the assistance from his guide dog Rocko without whose daily help this work would have been much more difficult. RGB acknowledges support from the Spanish Ministerio de Economía y Competitividad, through projects AYA2016-77846-P and AYA2014- 57490-P. RGB acknowledges support from the Spanish Ministerio de Economía y Competitividad, through project AYA2016-77846-P.OLD thanks the FAPESP and CNPq.

We derived two semi-empirical calibrations between the metallicity of the Narrow Line Region (NLR) of type-2 Active Galactic Nuclei and the rest-frame of the N V$��$1240/He II$\lambda1640$, C43=log[(C IV$\lambda1549$+C III]$\lambda1909$)/HeII$\lambda1640$] and C III]$\lambda1909$/C IV$\lambda1549$ emission-line intensity ratios. A metallicity-independent calibration between the ionization parameter and the C III]$\lambda1909$/C IV$\lambda1549$ emission-lines ratio was also derived. These calibrations were obtained comparing ratios of measured UV emission-line intensities, compiled from the literature, for a sample of 77 objects (redshift $0 \: < \: z \: < \: 3.8$) with those predicted by a grid of photoionization models built with the Cloudy code. Using the derived calibrations, it was possible to show that the metallicity estimations for NLRs are lower by a factor of about 2-3 than those for Broad Line Regions (BLRs). Besides we confirmed the recent result of the existence of a relation between the stellar mass of the host galaxy and its NLR metallicity. We also derived a $M-Z$ relation for the objects in our sample at $1.6 \: < \: z \: < \: 3.8$. This relation seems to follow the same trend as the ones estimated for Star Forming galaxies of similar high redshifts but for higher masses., 15 pages, MNRAS accepted

Integral field spectroscopy is well known for providing detailed insight of extended sources thanks to the possibility of handling space resolved spectroscopic information. Simple and straightforward analysis such as single line fitting yields interesting results, although it might miss a more complete picture in many cases. Violent star-forming regions, such as starburst galaxies, display very complex emission line profiles due to multiple kinematic components superposed in the line of sight. We perform a spatially resolved kinematical study of a single Green Pea (GP) galaxy, SDSS J083843.63+385350.5, using a new method for analysing integral field unit observations of emission line spectra. The method considers the presence of multiple components in the emission line profiles and makes use of a statistical indicator to determine the meaningful number of components to fit the observed profiles. We are able to identify three distinct kinematic features throughout the field and discuss their link with a rotating component, a strong outflow, and a turbulent mixing layer. We also derive an updated star formation rate for SDSS J0838 and discuss the link between the observed signatures of a large-scale outflow and of the Lyman continuum leakage detected in GP galaxies.© 2019 The Authors., VF acknowledges support from CONICYT Astronomy Program-2015 Research Fellow GEMINI-CONICYT (32RF0002). OLD is grateful to FAPESP and CNPq. ACK thanks the CNPq support.

We built a grid of photoionization models and compiled already available observational emission line intensities ($\rm 1000 \: < \: \lambda(\AA) \: < \: 2000$) of confirmed star formation regions and Active Galactic Nucleus (AGNs) in order to classify five Ly$\alpha$ emitter (LAE) objects at high redshift $(5.7 \: < \: z \: < \:7.2)$. We selected objects for which at least one metal emission-line was measured. The resulting sample is composed by the objects RXCJ2248.7-4431-ID3, HSCJ233408+004403, COSY, A1703-zd6, and CR7 (clump C). The photoionization models were built assuming a Power Law (associated with the presence of an AGN), a Direct Collapse Black Hole (DCBH), and Population II stars for the ionizing source. The resulting models were then compared with observational emission-line ratios in six diagnostic diagrams to produce a spectral classification of the sample. We found that CR7 (clump C), HSCJ233408+004403 and COSY probably have a non thermal ionizing source (AGN or DCBH) while the RXC J2248.7-4431-ID3 and A1703-zd6 seem to host a stellar cluster. Detailed photoionization models were constructed to reproduce observational emission line ratios of the sample of LAEs, and to derive chemical abundances and number of ionizing photons $Q(\rm H)$ of these objects. From these models, we found metallicities in the range $(Z/Z_{\odot})=0.1-0.5$ and $\log Q(\rm H) \: > \: 53$. Values for C/O abundance ratio derived for the LAEs seem to be consistent with those derived for local star forming objects with similar metallicities, while an overabundance of N/O was found for most of the LAEs., Comment: 32 pages, MNRAS accepted

We present Gemini Near-infrared Integral Field Spectrograph (NIFS) observations of the inner $1.5\times1.5$ kpc$^2$ of the narrow-line Seyfert 1 galaxy Mrk 42 at a spatial resolution of 60 pc and spectral resolution of 40 km s$^{-1}$. The emission-line flux and equivalent width maps clearly show a ring of circumnuclear star formation regions (CNSFRs) surrounding the nucleus with radius of $\sim$500 pc. The spectra of some of these regions show molecular absorption features which are probably of CN, TiO or VO, indicating the presence of massive evolved stars in the thermally pulsing asymptotic giant branch (TP-AGB) phase. The gas kinematics of the ring is dominated by rotation in the plane of the galaxy, following the large scale disk geometry, while at the nucleus an additional outflowing component is detected blueshifted by 300-500 kms$^{-1}$, relative to the systemic velocity of the galaxy. Based on the equivalent width of Br$\gamma$, we find evidences of gradients in the age of HII regions along the ring of Mrk 42, favoring the pearls on a string scenario of star formation. The broad component of Pa$\beta$ emission line presents a Full Width at Half Maximum (FWHM) of $\sim$1480 kms$^{-1}$, implying in a mass of $\sim\,2.5\times10^{6}$~M$_{\odot}$ for the central supermassive black hole. Based on emission-line ratios we conclude that besides the active galactic nucleus, Mrk 42 presents nuclear Starburst activity., Comment: 14 pages, MNRAS accepted

We calculate the effective temperature ($T_{\rm eff}$) of ionizing star(s), oxygen abundance of the gas phase $(\rm O/H)$, and the ionization parameter $U$ for a sample of H\,{\sc ii} regions located in the disks of 59 spiral galaxies in the 0.005 < z < 0.03 redshift range. We use spectroscopic data taken from the CALIFA data release 3 (DR3) and theoretical (for $T_{\rm eff}$ and $U$) and empirical (for O/H) calibrations based on strong emission-lines. We consider spatial distribution and radial gradients of those parameters in each galactic disk for the objects in our sample. Most of the galaxies in our sample ($\sim70$ \%) shows positive $T_{\rm eff}$ radial gradients even though some them exhibit negative or flat ones. The median value of the $T_{\rm eff}$ radial gradient is 0.762 kK/$R_{25}$. We find that radial gradients of both $\log U$ and $T_{\rm eff}$ depend on the oxygen abundance gradient, in the sense that the gradient of $\log U$ increases as $\log(\rm O/H)$ gradient increases while there is an anti-correlation between the gradient of $T_{\rm eff}$ and the oxygen abundance gradient. Moreover, galaxies with flat oxygen abundance gradients tend to have flat $\log U$ and $T_{\rm eff}$ gradients as well. Although our results are in agreement with the idea of the existence of positive $T_{\rm eff}$ gradients along the disk of the majority of spiral galaxies, this seems not to be an universal property for these objects., 11 pages, 11 figures; accepted for publication in MNRAS

We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active galactic nuclei (AGNs) estimated from the optical emission lines through the strong-line method (the theoretical calibration of Storchi-Bergmann et al. 1998), via the direct Te-method, and the central intersect abundances in the host galaxies determined from the radial abundance gradients. We found that the Te-method underestimates the oxygen abundances by up to ∼2 dex (with average value of ~0.8 dex) compared to the abundances derived through the strong-line method. This con- firms the existence of the so-called ?temperature problem? in AGNs. We also found that the abundances in the centres of galaxies obtained from their spectra trough the strong-line method are close to or slightly lower than the central intersect abun- dances estimated from the radial abundance gradient both in AGNs and Star-forming galaxies. The oxygen abundance of the NLR is usually lower than the maximum at- tainable abundance in galaxies (~2 times the solar value). This suggests that there is no extraordinary chemical enrichment of the NLRs of AGNs., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

We derive a new relation between the metallicity of Seyfert 2 active galactic nuclei (AGNs) and the intensity of the narrow emission-lines ratio N2O2 = log([N II] λ6584/[O II] λ3727). The calibration of this relation was performed by determining the metallicity (Z) of a sample of 58 AGNs through a diagram containing the observational data and the results of a grid of photoionization models obtained with the CLOUDY code. We find the new Z/Z⊙–N2O2 relation using the obtained metallicity values and the corresponding observational emission-line intensities for each object of the sample. Estimations derived through the use of this new calibration indicate that the narrow-line regions of Seyfert 2 galaxies exhibit a large range of metallicities (0.3 ≲ Z/Z⊙ ≲ 2.0), with a median value Z ≈ Z⊙. Regarding the possible existence of correlations between the luminosity L(Hβ), the electron density and the colour excess E(B − V) with the metallicity in this kind of objects, we do not find correlations between them., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

We obtained new quantitative determinations of the nitrogen abundance and a consistent relation between the nitrogen and oxygen abundances for a sample of Seyfert 2 galaxies located at redshift z < 0.1. We carried out this analysis using the CLOUDY code to build detailed photoionization models. We were able to reproduce observed optical narrow emission line intensities for 44 sources compiled from the literature. Our results show that Seyfert 2 nuclei have nitrogen abundances ranging from ∼0.3 to ∼7.5 times the solar value. We derived the relation log (N/H) = 1.05( ± 0.09) × [log (O/H)] − 0.35( ± 0.33). Results for N/O versus O/H abundance ratios derived for Seyfert 2 galaxies are in consonance with those recently derived for a sample of extragalactic disc H II regions with high metallicity., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

We have used observational spectroscopic data of star-forming regions compiled from the literature and photoionization models to analyse the neon ionic abundances obtained using both optical and mid-infrared emission lines. Comparing Ne++/H+ ionic abundances from distinct methods, we have found that, on average, the abundances obtained via infrared emission lines are higher than those obtained via optical lines, by a factor of 4. Photoionization models with abundance variations along the radius of the hypothetical nebula provide a possible explanation for a large part of the difference between ionic abundances via optical and infrared emission lines. The ionization correction factor (ICF) for the neon is obtained from direct determinations of ionic fractions using infrared emission lines. We derive a constant Ne/O ratio (log Ne/O ≈ -0.70) for a large range of metallicities, independently of the ICF used to compute the neon total abundance., Facultad de Ciencias Astronómicas y Geofísicas

We study the kinematics and excitation mechanisms of H 2 and [Fe ii] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (0.8–2.4 μm) spectroscopy together with new photoionization models. H 2 emission lines are systematically narrower than narrow-line region lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star-forming galaxies. The importance of the thermal excitation in star-forming galaxies may be associated with the presence of supernova remnants close to the region emitting H 2 lines. This hypothesis is further supported by the similarity between vibrational and rotational temperatures of H 2 . We confirm that the diagram involving the line ratios H 2 2.121 μm/Brγ and [Fe ii] 1.257 μm/Paβ is an efficient tool for separating emission-line objects according to their dominant types of activities. We suggest new limits to the line ratios in order to discriminate between the different types of nuclear activities.

The effective temperature (Teff) of the radiation field of the ionizing star(s) of a large sample of extragalactic HII regions was estimated using the R = log([O II] (λλ3726 + 29)/[O III] λ5007) index. We used a grid of photoionization models to calibrate the Teff-R relation finding that it has a strong dependence with the ionizing parameter, while it shows a weak direct dependence with the metallicity (variations in Z imply variations in U) of both the stellar atmosphere of the ionizing star and the gas phase of the HII region. Since the R index varies slightly with the Teff for values larger than 40 kK, the R index can be used to derive the Teff in the 30-40 kK range. A large fraction of the ionization parameter variation is due to differences in the temperature of the ionizing stars and then the use of the (relatively) low Teff dependent S2 = [S II] (λλ6717 + 31)/Hα emission-line ratio to derive the ionization parameter is preferable over others in the literature. We propose linear metallicity dependent relationships between S2 and U. Teff and metallicity estimations for a sample of 865 HII regions, whose emission-line intensities were compiled from the literature, do not show any Teff-Z correlation. On the other hand, it seems to be hints of the presence of an anticorrelation between Teff-U.We found that the majority of the studied HII regions (~87 per cent) present Teff values in the range between 37 and 40 kK, with an average value of 38.5(±1) kK. We also studied the variation of Teff as a function of the galactocentric distance for 14 spiral galaxies. Our results are in agreement with the idea of the existence of positive Teff gradients along the disc of spiral galaxies., Instituto de Astrofísica de La Plata

In this work, we used a grid of photoionization models combined with stellar population synthesis models to derive reliable ionization correction factors (ICFs) for the sulphur in star-forming regions. These models cover a large range of nebular parameters and yielding ionic abundances in consonance with those derived through optical and infrared observational data of star-forming regions. From our theoretical ICFs, we suggested an α value of 3.27 ± 0.01 in the classical Stasińska formulae. We compared the total sulphur abundance in the gas phase of a large sample of objects by using our theoretical ICF and other approaches. In average, the differences between the determinations via the use of the different ICFs considered are similar to the uncertainties in the S/H estimations. Nevertheless, we noted that for some objects it could reach up to about 0.3 dex for the low-metallicity regime. Despite of the large scatter of the points, we found a trend of S/O ratio to decrease with the metallicity, independently of the ICF used to compute the sulphur total abundance., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

We analyze the reliability of oxygen abundances and ionization parameters obtained from different diagnostic diagrams. For this, we compiled from the literature observational emission line intensities and oxygen abundance of 446 star-forming regions whose O/H abundance was determined by direct estimation of electron temperature. The abundances compiled were compared with the values calculated in this work using different diagnostic diagrams in combination with results from a grid of photoionization models. We found that the [\ion{O}{iii}]/[\ion{O}{ii}] vs. [\ion{N}{ii}]/[\ion{O}{ii}], [\ion{O}{iii}]/H$\beta$ vs. [\ion{N}{ii}]/[\ion{O}{ii}], and ([\ion{O}{iii}]/H$\beta$)/([\ion{N}{ii}]/H$\alpha$) vs. [\ion{S}{ii}]/[\ion{S}{iii}] diagnostic diagrams give O/H values close to the $T_{\rm e}$-method, with differences of about 0.04 dex and dispersion of about 0.3 dex. Similar results were obtained by detailed models but with a dispersion of 0.08 dex. The origin of the dispersion found in the use of diagnostic diagrams is probably due to differences between the real N/O-O/H relation of the sample and the one assumed in the models. This is confirmed by the use of detailed models that do not have a fixed N/O-O/H relation. We found no correlation between ionization parameter and the metallicity for the objects of our sample. We conclude that the combination of two line ratio predicted by photoionization models, one sensitive to the metallicity and another sensitive to the ionization parameter, which takes into account the physical conditions of star-forming regions, gives O/H estimates close to the values derived using direct detections of electron temperatures.

Aims. To derive O/H, N/O, and S/O abundances of Hll regions located in nine Virgo spiral galaxies, as well as to verify what is the cause of the abundance segregation found. Methods. We employed photoionization models to reproduce observed emission-line intensities of H II regions located in the galaxies considered. The abundance gradients obtained were interpreted using a grid of chemical evolution models. Results. Our models indicate that galaxies near to the core of the Virgo cluster are overabundant in O/H, N/O, and S/O by about 0.25 dex in comparison to the ones at the periphery. With one exception, models with upper stellar mass limit of M u = 30-40 M Θ and age of the ionizing star cluster ranging from 1.5 to 2.5 Myr were able to reproduce the observational data. Chemical models indicate the collapse time-scale for inner regions of galaxies near to the Virgo core is larger than the one in galaxies located at the intermediate and peripheral positions in the cluster, what can be due to the dense environment existing in Virgo Cluster core.

We used photoionization models in order to reproduce the observed gradients of emission-line ratios for H  regions located in the normal spiral galaxy M 101 and in three barred spiral galaxies, namely NGC 1365, NGC 925, and NGC 1073. The behavior of the following nebular parameters across the disk of these galaxies was determined: temperature of the ionizing star (Teff), ionization parameter (U), and the abundance ratios O/H, N/O, and S/O. Our O/H predictions were found to be consistent with some empirical abundance determinations, but are overestimated by a factor of 0.1−0.4 dex when compared to the direct abundance determinations. NGC 1073 seems to be overabundant in nitrogen compared to other spiral galaxies. No gradient of S/O was found in the studied galaxies, and we derived a positive Teff gradient ofTeff/� R = (400 ± 112) K kpc −1 and U ranging from −3. 0t o−2.3. The N/ Ov s. O/H diagram in general is consistent with chemical evolution models that assume that the nitrogen synthesis has both a primary and a secondary component compared to oxygen. However, a very strong N/O dependence on the O/H at high abundance was found.

The determination of temperature ( T eff ) of the ionizing stars of HII regions was considered. In this work we used photoionization models for HII regions ionized by a single star to show that the index $R=\log\,$([$\ion{O}{ii}$]$\lambda\lambda$3726+3729/[$\ion{O}{iii}$] λ 5007) can be used to estimate T eff . The relation R vs. T eff proved to be rather independent of the chemical abundances, but strongly dependent on the ionization parameter of the nebula. In order to check the reliability of using R for temperature determination, we compared the values of T eff obtained via the index R for a sample of HII regions with data available in the literature with independent estimations.

We present an observational study about the impacts of the interactions on the electron density of HII regions located in seven systems of interacting galaxies. The data consist of long-slit spectra in the range 4400-7300 Å, obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS-S). The electron density was determined using the ratio of emission lines [S II] λ6716/λ6731. Our results indicate that the electron density estimates obtained of HII regions from our sample of interacting galaxies are systematically higher than those derived for isolated galaxies. The mean electron density values of interacting galaxies are in the range of Ne = 24-532 cm-3, while those obtained for isolated galaxies are in the range of Ne =40-137 cm-3.Comparing the observed emission lines with predictions of photoionization models, we verified that almost all the HII regions of the galaxies AM 1054A, AM 2058B and AM 2306B have emission lines excited by shock gas. For the remaining galaxies, only few H II regions have emission lines excited by shocks, such as in AM 2322B (one point) and AM 2322A (four points). No correlation is obtained between the presence of shocks and electron densities. Indeed, the highest electron density values found in our sample do not belong to the objects with gas shock excitation. We emphasize the importance of considering these quantities especially when the metallicity is derived for these types of systems., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

We analyzed the evolution of the metallicity of the gas with the redshift for a sample of AGNs in a very wide redshift range (0, Comment: 25 pages, 10 figures, accepted MNRAS

Interactions between galaxies are very common. There are special kinds of interactions that produce systems called Polar Ring Galaxies (PRGs), composed by a lenticular, elliptical, or spiral host galaxy, surrounded by a ring of stars and gas, orbiting in an approximately polar plane. The present work aims to study AM2020-504, a PRG with an elliptical host galaxy, and a narrow and well defined ring, probably formed by accretion of material from a donor galaxy, collected by the host galaxy. Our observational study was based on BVRI broad band imagery as well as longslit spectroscopy in the wavelenght range 4100--8600\AA, performed at the 1.6m telescope at the Observat\'orio do Pico dos Dias (OPD), Brazil. We estimated a redshift of z= 0.01683, corresponding a heliocentric radial velocity of 5045 +/-23 km/s. The (B-R) color map shows that the ring is bluer than the host galaxy, indicating that the ring is a younger structure. Standard diagnostic diagrams were used to classify the main ionizing source of selected emission-line regions (nucleus, host galaxy and ring). It turns out that the ring regions are mainly ionized by massive stars while the nucleus presents AGN characteristics. Using two empirical methods, we found oxygen abundances for the HII regions located in the ring in the range 12+log(O/H)=8.3-8.8 dex, the presence of an oxygen gradient across the ring, and that AM2020-504 follows the metallicity-luminosity relation of spiral galaxies. These results support the accretion scenario for this object and rules out cold accretion as source for the HI gas in the polar ring.

We use near-infrared spectroscopic data from the inner few hundred parsecs of a sample of 47 active galaxies to investigate possible correlations between the stellar velocity dispersion (sigma_star), obtained from the fit of the K-band CO stellar absorption bands, and the gas velocity dispersion (sigma) obtained from the fit of the emission-line profiles of [SIII]0.953um, [Fe II]1.257um, [FeII]1.644um and H_2 2.122um. While no correlations with sigma_star were found for H_2 and [SIII], a good correlation was found for the two [Fe II] emission lines, expressed by the linear fit sigma_star = 95.4\pm16.1 + (0.25\pm0.08)sigma_[Fe II]. Excluding barred objects from the sample a better correlation is found between sigma_star and sigma_[FeII], with a correlation coefficient of R=0.80 and fitted by the following relation: sigma_\star = 57.9\pm23.5 + (0.42\pm0.10)sigma_[FeII]. This correlation can be used to estimate $\sigma_\star$ in cases it cannot be directly measured and the [FeII] emission lines are present in the spectra, allowing to obtain the mass of the supermassive black hole (SMBH) from the M-\sigma_\star relation. The scatter from a one-to-one relationship between sigma_star and its value derived from sigma_[FeII] using the equation above for our sample is 0.07dex, which is smaller than that obtained in previous studies which use \sigma_[OIII] in the optical as a proxy for sigma_star. The use of sigma_[Fe\,II] in the near-IR instead of sigma_[OIII] in the optical is a valuable option for cases in which optical spectra are not available or are obscured, as is the case of many AGN., Comment: accepted for publication in MNRAS

We present an observational study about the impacts of the interactions in the kinematics, stellar populations, and oxygen abundances of the components of the galaxy pair AM\,2322-821. A fairly symmetric rotation curve for the companion (AM\,2322B) galaxy with a deprojected velocity amplitude of 110 km s$^{-1}$ was obtained, and a dynamical mass of $ 1.1 - 1.3 \times 10^{10} M_{\sun}$ within a radius of 4 kpc was estimated using this deprojected velocity. Asymmetries in the radial velocity field were detected for the companion, very likely due the interaction between the galaxies. The interaction between the main and companion galaxies was modelled using numerical N-body/hydrodynamical simulations, with the result indicating that the current stage of the system would be about 90 Myr after perigalacticum. The spatial variation in the distribution of the stellar-population components in both galaxies was analysed using the stellar population synthesis code {\sc STARLIGHT}. The companion galaxy is dominated by a very young (t $ \leq 1\times10^{8}$ yr) population, with the fraction of this population to the total flux at $\lambda\, 5\,870\, \AA$, increasing outwards in the galaxy disc. On the other hand, the stellar population of AM\,2322A is heterogeneous along the slit positions observed. Spatial profiles of oxygen abundance in the gaseous phase were obtained using the diagnostic diagram R23 vs. [OIII]/[OII], where we compared the observed values with the ones obtained from photoionization models. Such gradients of oxygen abundance are significantly flatter for this pair of galaxies than in typical isolated spiral galaxies. This metallicity distribution is interpreted as the gradients having been destroyed by interaction-induced gas flows from the outer parts to the centre of the galaxy

We study the kinematics and excitation mechanisms of H2 and [Fe II] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (NIR, 0.8-2.4 micrometers) spectroscopy together with new photoionisation models. H2 emission lines are systematically narrower than narrow-line region (NLR) lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star forming galaxies. The importance of the thermal excitation in star forming galaxies may be associated with the presence of supernova remnants close to the region emitting H2 lines. This hypothesis is further supported by the similarity between the vibrational and rotational temperatures of H2. We confirm that the diagram involving the line ratios H2 2.121/Br_gamma and [Fe II] 1.257/Pa_beta is an efficient tool for separating emission-line objects according to their dominant type of activity. We suggest new limits to the line ratios in order to discriminate between the different types of nuclear activity.