Changing-look active galactic nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the early data

Wei Jian Guo*, Hu Zou, Victoria A. Fawcett, Rebecca Canning, Stephanie Juneau, Tamara M. Davis, David M. Alexander, Linhua Jiang, Jessica Nicole Aguilar, Steven Ahlen, David Brooks, Todd Claybaugh, Axel de la Macorra, Peter Doel, Kevin Fanning, Jaime E. Forero-Romero, Satya Gontcho A Gontcho, Klaus Honscheid, Theodore Kisner, Anthony KreminMartin Landriau, Aaron Meisner, Ramon Miquel, John Moustakas, Jundan Nie, Zhiwei Pan, Claire Poppett, Francisco Prada, Mehdi Rezaie, Graziano Rossi, Małgorzata Siudek, Eusebio Sanchez, Michael Schubnell, Hee Jong Seo, Jipeng Sui, Gregory Tarlé, Zhimin Zhou

*Corresponding author for this work

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Abstract

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.

Original languageEnglish
Article number26
Number of pages18
JournalAstrophysical Journal, Supplement Series
Volume270
Issue number2
Early online date29 Jan 2024
DOIs
Publication statusPublished - 1 Feb 2024

Keywords

  • active galaxies
  • accretion
  • active galactic nuclei
  • supermassive black holes
  • cataalogs

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