Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs?
In the manuscript, we check properties of electron densities n _e traced by flux ratio R _sii of [S ii ] λ 6716 Å to [S ii ] λ 6731 Å in narrow emission line regions (NLRs) between Type-1 active galactic nucleus (AGN) and Type-2 AGN in SDSS Data Release 12 (DR12). Under the framework of unified mode...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad029a |
| _version_ | 1827390925011156992 |
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| author | XueGuang Zhang |
| author_facet | XueGuang Zhang |
| author_sort | XueGuang Zhang |
| collection | DOAJ |
| description | In the manuscript, we check properties of electron densities n _e traced by flux ratio R _sii of [S ii ] λ 6716 Å to [S ii ] λ 6731 Å in narrow emission line regions (NLRs) between Type-1 active galactic nucleus (AGN) and Type-2 AGN in SDSS Data Release 12 (DR12). Under the framework of unified model considering kiloparsec-scale structures, similar n _e in NLRs should be expected between Type-1 AGN and Type-2 AGN. Based on reliable measurements of the [S ii ] doublet with measured parameters at least 5 times larger than corresponding uncertainties, there are 6039 Type-1 AGN and 8725 Type-2 AGN (excluding the Type-2 LINERs and the composite galaxies) collected from SDSS DR12. Then, lower R _sii (higher n _e ) in NLRs can be well confirmed in Type-1 AGN than in Type-2 AGN, with the confidence level higher than 5 σ , even after considering the necessary effects including effects of electron temperatures traced by [O iii ] λ 4364,4959,5007 Å on estimating n _e in NLRs. Two probable methods are proposed to explain the higher n _e in NLRs in Type-1 AGN. First, the higher n _e in NLRs of Type-1 AGN could indicate longer time durations of AGN activities in Type-1 AGN than in Type-2 AGN, if AGN activities triggering galactic-scale outflows leading to more electrons injecting into NLRs were accepted to explain the higher n _e in NLRs of Type-2 AGN than H ii galaxies. Second, the lower n _e in NLRs of Type-2 AGN could be explained by stronger star-forming contributions in Type-2 AGN, considering lower n _e in H ii regions. The results provide interesting challenges to the commonly and widely accepted unified model of AGN. |
| first_indexed | 2024-03-08T17:02:07Z |
| format | Article |
| id | doaj.art-93d367baa0b14af183c5a5bbe22da35e |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T17:02:07Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-93d367baa0b14af183c5a5bbe22da35e2024-01-04T09:29:05ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01960210810.3847/1538-4357/ad029aAre There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs?XueGuang Zhang0https://orcid.org/0000-0001-5458-8354Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, GuangXi University , No. 100, Daxue Road, Nanning 530004, People’s Republic of China ; xgzhang@gxu.edu.cnIn the manuscript, we check properties of electron densities n _e traced by flux ratio R _sii of [S ii ] λ 6716 Å to [S ii ] λ 6731 Å in narrow emission line regions (NLRs) between Type-1 active galactic nucleus (AGN) and Type-2 AGN in SDSS Data Release 12 (DR12). Under the framework of unified model considering kiloparsec-scale structures, similar n _e in NLRs should be expected between Type-1 AGN and Type-2 AGN. Based on reliable measurements of the [S ii ] doublet with measured parameters at least 5 times larger than corresponding uncertainties, there are 6039 Type-1 AGN and 8725 Type-2 AGN (excluding the Type-2 LINERs and the composite galaxies) collected from SDSS DR12. Then, lower R _sii (higher n _e ) in NLRs can be well confirmed in Type-1 AGN than in Type-2 AGN, with the confidence level higher than 5 σ , even after considering the necessary effects including effects of electron temperatures traced by [O iii ] λ 4364,4959,5007 Å on estimating n _e in NLRs. Two probable methods are proposed to explain the higher n _e in NLRs in Type-1 AGN. First, the higher n _e in NLRs of Type-1 AGN could indicate longer time durations of AGN activities in Type-1 AGN than in Type-2 AGN, if AGN activities triggering galactic-scale outflows leading to more electrons injecting into NLRs were accepted to explain the higher n _e in NLRs of Type-2 AGN than H ii galaxies. Second, the lower n _e in NLRs of Type-2 AGN could be explained by stronger star-forming contributions in Type-2 AGN, considering lower n _e in H ii regions. The results provide interesting challenges to the commonly and widely accepted unified model of AGN.https://doi.org/10.3847/1538-4357/ad029aActive galaxiesActive galactic nucleiEmission line galaxiesSeyfert galaxies |
| spellingShingle | XueGuang Zhang Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? The Astrophysical Journal Active galaxies Active galactic nuclei Emission line galaxies Seyfert galaxies |
| title | Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? |
| title_full | Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? |
| title_fullStr | Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? |
| title_full_unstemmed | Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? |
| title_short | Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs? |
| title_sort | are there higher electron densities in narrow emission line regions of type 1 agns than in type 2 agns |
| topic | Active galaxies Active galactic nuclei Emission line galaxies Seyfert galaxies |
| url | https://doi.org/10.3847/1538-4357/ad029a |
| work_keys_str_mv | AT xueguangzhang aretherehigherelectrondensitiesinnarrowemissionlineregionsoftype1agnsthanintype2agns |