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Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data

Lookup NU author(s): Dr Vicky FawcettORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2024. The Author(s). Published by the American Astronomical Society.Changing-look active galactic nuclei (CL AGNs) can be generally confirmed by the emergence (turn-on) or disappearance (turn-off) of broad emission lines (BELs), associated with a transient timescale (about 100 ∼ 5000 days) that is much shorter than predicted by traditional accretion disk models. We carry out a systematic CL AGN search by crossmatching the spectra coming from the Dark Energy Spectroscopic Instrument and the Sloan Digital Sky Survey. Following previous studies, we identify CL AGNs based on Hα, Hβ, and Mg ii at z ≤ 0.75 and Mg ii, C iii], and C iv at z > 0.75. We present 56 CL AGNs based on visual inspection and three selection criteria, including 2 Hα, 34 Hβ, 9 Mg ii, 18 C iii], and 1 C iv CL AGN. Eight cases show simultaneous appearances/disappearances of two BELs. We also present 44 CL AGN candidates with significant flux variation of BELs, but remaining strong broad components. In the confirmed CL AGNs, 10 cases show additional CL candidate features for different lines. In this paper, we find: (1) a 24:32 ratio of turn-on to turn-off CL AGNs; (2) an upper-limit transition timescale ranging from 330 to 5762 days in the rest frame; and (3) the majority of CL AGNs follow the bluer-when-brighter trend. Our results greatly increase the current CL census (∼30%) and would be conducive to exploring the underlying physical mechanism.

Publication metadata

Author(s): Guo W-J, Zou H, Fawcett VA, Canning R, Juneau S, Davis TM, Alexander DM, Jiang L, Aguilar JN, Ahlen S, Brooks D, Claybaugh T, de la Macorra A, Doel P, Fanning K, Forero-Romero JE, Gontcho A Gontcho S, Honscheid K, Kisner T, Kremin A, Landriau M, Meisner A, Miquel R, Moustakas J, Nie J, Pan Z, Poppett C, Prada F, Rezaie M, Rossi G, Siudek M, Sanchez E, Schubnell M, Seo H-J, Sui J, Tarle G, Zhou Z

Publication type: Article

Publication status: Published

Journal: Astrophysical Journal, Supplement Series

Year: 2024

Volume: 270

Issue: 2

Print publication date: 01/02/2024

Online publication date: 29/01/2024

Acceptance date: 18/11/2023

Date deposited: 20/02/2024

ISSN (print): 0067-0049

ISSN (electronic): 1538-4365

Publisher: American Astronomical Society

URL: https://doi.org/10.3847/1538-4365/ad118a

DOI: 10.3847/1538-4365/ad118a

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