2025/04/26 by XueGuang, Zhang
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.2504.18892
openalex publication_date 2025/04/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/03
In this manuscript, we report evidence to support the dependence of D\it n4000 (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 n4000 and flux ratios of [O~\sc iii] to narrow Hβ (O3HB) and [N~\sc ii] to narrow Hα (N2HA) and narrow Hα line luminosity LHα, linear dependence of the D\it n4000 on the O3HB, N2HA and LHα in the local Type-2 AGN can provide clues to support the dependence of D\it n4000 on properties of narrow emission lines. Linear correlations between the D\it n4000 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 n4000 on the LHα can be confirmed in Type-2 AGN, with Spearman rank correlation coefficient about -0.7. Moreover, combining the LHα and the N2HA, a more robust and stronger linear correlation can be confirmed between the D\it n4000 and the new parameter LR=0.2log(LHα)-0.5log(\rm N2HA), with Spearman rank correlation coefficient about -0.76 and with smaller RMS scatters. After considering necessary effects, the dependence of D\it n4000 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.