Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4
We derive oxygen abundances for two samples of Seyfert 2 (Sy2) active galactic nuclei (AGNs) selected from the KPNO International Spectroscopic Survey (KISS). The two samples from KISS include 17 intermediate-redshift (0.29 ≤ z ≤ 0.42) Sy2s detected via their [O iii ] lines, and 35 low-redshift ( z...
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/aced91 |
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| author | David J. Carr John J. Salzer Caryl Gronwall Anna L. Williams |
| author_facet | David J. Carr John J. Salzer Caryl Gronwall Anna L. Williams |
| author_sort | David J. Carr |
| collection | DOAJ |
| description | We derive oxygen abundances for two samples of Seyfert 2 (Sy2) active galactic nuclei (AGNs) selected from the KPNO International Spectroscopic Survey (KISS). The two samples from KISS include 17 intermediate-redshift (0.29 ≤ z ≤ 0.42) Sy2s detected via their [O iii ] lines, and 35 low-redshift ( z ≤ 0.1), H α -detected Sy2s. The primary goal of this work is to explore whether the metallicity distribution of these two samples changes with redshift. To determine the oxygen abundances of the KISS galaxies, we use Cloudy to create a large number of photoionization model grids by varying the temperature of the accretion disk, the ratio of X-ray to UV continuum light, the ionization parameter, the hydrogen density, and the metallicity of the narrow-line region clouds. We link the results of these models to the observed [O iii ]/H β and [N ii ]/H α emission-line ratios of the KISS sample on a Baldwin–Philips–Terlevich diagram, interpolating across the model grids to derive metallicity. The two redshift samples overlap substantially in terms of derived metal abundances, but we find that some of the intermediate-redshift Sy2s possess lower abundances than their local universe counterparts. Our analysis provides evidence for modest levels of chemical evolution (0.18 ± 0.06 dex) over 3–4 Gyr of look-back time. We compare our results to other AGN abundance derivation methods from the literature. |
| first_indexed | 2024-03-11T21:30:45Z |
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| id | doaj.art-59c59f6cae374bffb046d0fe7c8bdbb4 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T21:30:45Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj.art-59c59f6cae374bffb046d0fe7c8bdbb42023-09-27T09:40:20ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01955214110.3847/1538-4357/aced91Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4David J. Carr0https://orcid.org/0000-0002-4876-5382John J. Salzer1https://orcid.org/0000-0001-8483-603XCaryl Gronwall2https://orcid.org/0000-0001-6842-2371Anna L. Williams3Department of Astronomy, Indiana University , 727 East Third Street, Bloomington, IN 47405, USA ; davidjcarr94@gmail.comDepartment of Astronomy, Indiana University , 727 East Third Street, Bloomington, IN 47405, USA ; davidjcarr94@gmail.comDepartment of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation & the Cosmos, The Pennsylvania State University , University Park, PA 16802, USADepartment of Physics & Astronomy, Macalester College , 1600 Grand Avenue, Saint Paul, MN 55105, USAWe derive oxygen abundances for two samples of Seyfert 2 (Sy2) active galactic nuclei (AGNs) selected from the KPNO International Spectroscopic Survey (KISS). The two samples from KISS include 17 intermediate-redshift (0.29 ≤ z ≤ 0.42) Sy2s detected via their [O iii ] lines, and 35 low-redshift ( z ≤ 0.1), H α -detected Sy2s. The primary goal of this work is to explore whether the metallicity distribution of these two samples changes with redshift. To determine the oxygen abundances of the KISS galaxies, we use Cloudy to create a large number of photoionization model grids by varying the temperature of the accretion disk, the ratio of X-ray to UV continuum light, the ionization parameter, the hydrogen density, and the metallicity of the narrow-line region clouds. We link the results of these models to the observed [O iii ]/H β and [N ii ]/H α emission-line ratios of the KISS sample on a Baldwin–Philips–Terlevich diagram, interpolating across the model grids to derive metallicity. The two redshift samples overlap substantially in terms of derived metal abundances, but we find that some of the intermediate-redshift Sy2s possess lower abundances than their local universe counterparts. Our analysis provides evidence for modest levels of chemical evolution (0.18 ± 0.06 dex) over 3–4 Gyr of look-back time. We compare our results to other AGN abundance derivation methods from the literature.https://doi.org/10.3847/1538-4357/aced91Active galactic nucleiSeyfert galaxiesEmission line galaxiesChemical abundancesCosmological evolutionGalaxies |
| spellingShingle | David J. Carr John J. Salzer Caryl Gronwall Anna L. Williams Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 The Astrophysical Journal Active galactic nuclei Seyfert galaxies Emission line galaxies Chemical abundances Cosmological evolution Galaxies |
| title | Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 |
| title_full | Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 |
| title_fullStr | Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 |
| title_full_unstemmed | Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 |
| title_short | Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3–0.4 |
| title_sort | metal abundances of intermediate redshift active galactic nuclei evidence for a population of lower metallicity seyfert 2 galaxies at z 0 3 0 4 |
| topic | Active galactic nuclei Seyfert galaxies Emission line galaxies Chemical abundances Cosmological evolution Galaxies |
| url | https://doi.org/10.3847/1538-4357/aced91 |
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