Dependence of 4000Å~ break strength on narrow emission line properties in local Type-2 AGN
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arXiv
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| Formato: | Preprint |
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2025
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| _version_ | 1866915261621207040 |
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| author | XueGuang, Zhang |
| author_facet | XueGuang, Zhang |
| contents | In this manuscript, we report evidence to support the dependence of D{\it n}4000 (4000Å~ break strength to trace stellar ages) on central AGN activity traced by narrow emission line properties in local Type-2 AGN in SDSS DR16. Based on the measured D{\it n}4000 and flux ratios of [O~{\sc iii}] to narrow H$β$ (O3HB) and [N~{\sc ii}] to narrow H$α$ (N2HA) and narrow H$α$ line luminosity $L_{Hα}$, linear dependence of the D{\it n}4000 on the O3HB, N2HA and $L_{Hα}$ in the local Type-2 AGN can provide clues to support the dependence of D{\it n}4000 on properties of narrow emission lines. Linear correlations between the D{\it n}4000 and the O3HB and N2HA can be found in the local Type-2 AGN, with Spearman rank correlations about -0.39 and 0.53. Meanwhile, stronger dependence of the D{\it n}4000 on the $L_{Hα}$ can be confirmed in Type-2 AGN, with Spearman rank correlation coefficient about -0.7. Moreover, combining the $L_{Hα}$ and the N2HA, a more robust and stronger linear correlation can be confirmed between the D{\it n}4000 and the new parameter $LR=0.2\log(L_{Hα})-0.5\log(\rm N2HA)$, with Spearman rank correlation coefficient about -0.76 and with smaller RMS scatters. After considering necessary effects, the dependence of D{\it n}4000 on $LR$ is stable and robust enough for the local Type-2 AGN, indicating the $LR$ on the narrow emission lines can be treated as a better indicator to statistically trace stellar ages of samples of more luminous AGN with weaker host galaxy absorption features. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_18892 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Dependence of 4000Å~ break strength on narrow emission line properties in local Type-2 AGN XueGuang, Zhang Astrophysics of Galaxies In this manuscript, we report evidence to support the dependence of D{\it n}4000 (4000Å~ break strength to trace stellar ages) on central AGN activity traced by narrow emission line properties in local Type-2 AGN in SDSS DR16. Based on the measured D{\it n}4000 and flux ratios of [O~{\sc iii}] to narrow H$β$ (O3HB) and [N~{\sc ii}] to narrow H$α$ (N2HA) and narrow H$α$ line luminosity $L_{Hα}$, linear dependence of the D{\it n}4000 on the O3HB, N2HA and $L_{Hα}$ in the local Type-2 AGN can provide clues to support the dependence of D{\it n}4000 on properties of narrow emission lines. Linear correlations between the D{\it n}4000 and the O3HB and N2HA can be found in the local Type-2 AGN, with Spearman rank correlations about -0.39 and 0.53. Meanwhile, stronger dependence of the D{\it n}4000 on the $L_{Hα}$ can be confirmed in Type-2 AGN, with Spearman rank correlation coefficient about -0.7. Moreover, combining the $L_{Hα}$ and the N2HA, a more robust and stronger linear correlation can be confirmed between the D{\it n}4000 and the new parameter $LR=0.2\log(L_{Hα})-0.5\log(\rm N2HA)$, with Spearman rank correlation coefficient about -0.76 and with smaller RMS scatters. After considering necessary effects, the dependence of D{\it n}4000 on $LR$ is stable and robust enough for the local Type-2 AGN, indicating the $LR$ on the narrow emission lines can be treated as a better indicator to statistically trace stellar ages of samples of more luminous AGN with weaker host galaxy absorption features. |
| title | Dependence of 4000Å~ break strength on narrow emission line properties in local Type-2 AGN |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2504.18892 |