Chemical abundances of Seyfert 2 AGNs, I: comparing oxygen abundances from distinct methods using SDSS

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<~0.4). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPACExtragalactic Database (NED) to selected optical (3000Fil: Dors, Oli L.. Universidade Do Vale Do Paraiba; BrasilFil: de Freitas Rosa, Morsyleide. Universidade Do Vale Do Paraiba; BrasilFil: Amores, E. B.. Universidade Estadual de Feira de Santana; BrasilFil: Almarcha Pérez, Martha Ayelén. Instituto de Astrofísica de Andalucía - Csic; EspañaFil: Cardaci, Monica Viviana. Instituto de Astrofísica de la Plata (conicet- Universidad Nacional de la Plata); Argentina. Universidad Nacional de La Plata; ArgentinaFil: Hägele, Guillermo Federico. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Armah, M.. Universidade Do Vale Do Paraiba; BrasilFil: Krabbe, A. C.. Universidade Do Vale Do Paraiba; BrasilFil: Ruiz Faúndez, Giovanni Patricio. Laboratorio Nacional de Astrofisica, Itajuba; Brasi

Chemical abundances of Seyfert 2 AGNs - I. Comparing oxygen abundances from distinct methods using SDSS

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<~0.4). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPACExtragalactic Database (NED) to selected optical (3000<γ(Å)<7000) emission line intensities of 463 confirmed Seyfert 2 AGNs. The oxygen abundances of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the Bayesian H II-CHI-MISTRY code and the Te-method.We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ~0.8 dex, with the largest discrepancies in the low-metallicity regime (12 + log(O/H) <~ 8.5).We confirmed that the Te-method underestimates the oxygen abundance in NLRs, producing unreal subsolar values. We did not find any correlation between the stellar mass of the host galaxies and the metallicity of their AGNs. This result is independent of the method used to estimate Z. © 2019 The Author(s).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.Peer reviewe