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Lookup NU author(s): Dr Vicky FawcettORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025. The Author(s). Published by the American Astronomical Society. From a parent catalog of 561 changing-look active galactic nuclei (CL-AGNs) identified by W.-J. Guo et al., we investigate the evolutionary sequence of broad emission lines using a redshift-selected subset (0.35 < z < 0.45) of 54 CL-AGNs whose Dark Energy Spectroscopic Instrument (DESI) spectra simultaneously cover the Hα, Hβ, and Mg ii emission lines. To provide a baseline for comparison, we construct a control sample of 19,897 normal Type 1 AGNs within the same redshift range from the DESI Year 1 data. Through stacked spectral analysis and line-continuum luminosity correlations, we identify a clear evolutionary sequence in all AGNs where broad Hβ fades first, followed by Mg ii, and then Hα, as the AGN luminosity declines—consistent with expectations from reverberation mapping. This trend reflects a radially stratified broad-line region (BLR), where each line’s responsivity depends on its ionization potential and radial distance from the central engine. In addition, we find that more massive supermassive black holes require lower Eddington ratios to fully suppress broad emission lines, suggesting that the critical accretion threshold for the changing-look phenomenon is mass-dependent. Our results present the first statistical confirmation of a stratified broad-line fading sequence in AGNs, reinforcing the central role of accretion state in shaping BLR structure and visibility.
Author(s): Guo W-J, Fawcett VA, Siudek M, Li Y-R, Cheng C, Panda S, Pan Z, Sun S, Greenwell CL, Alexander DM, Moustakas J, Zhai S, Jin J-J, Cheng H, Hu J, Chen Y-J, Zhang Z-X, Wang J-M
Publication type: Article
Publication status: Published
Journal: Astrophysical Journal
Year: 2025
Volume: 995
Issue: 2
Print publication date: 20/12/2025
Online publication date: 11/12/2025
Acceptance date: 08/11/2025
Date deposited: 08/04/2026
ISSN (print): 0004-637X
ISSN (electronic): 1538-4357
Publisher: American Astronomical Society
URL: https://doi.org/10.3847/1538-4357/ae1d7b
DOI: 10.3847/1538-4357/ae1d7b
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