Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. II. Statistical Properties from the First Data Release
Wei-Jian Guo, Hu Zou, Claire Greenwell, D. M. Alexander, Victoria A. Fawcett, Zhiwei Pan, M. Siudek, J. Aguilar, S. P. Ahlen, D. Brooks, T. Claybaugh, Kyle Dawson, Axel de la Macorra, P. Doel, Andreu Font-Ribera, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutiérrez, R. Kehoe, Theodore Kisner, Martin Landriau, L. Le Guillou, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Francisco Prada, Graziano Rossi, E. Sánchez, M. Schubnell, David Sprayberry, Jipeng Sui, G. Tarlé, Benjamin Alan Weaver, Yun-Ao Xiao, Siwei Zou
Abstract
Abstract We present the identification of changing-look active galactic nuclei (CL-AGNs) from the Dark Energy Spectroscopic Instrument First Data Release and Sloan Digital Sky Survey Data Release 16 at z ≤ 0.9. To confirm the CL-AGNs, we utilize spectral flux calibration assessment via an [O iii ]-based calibration, pseudophotometry examination, and visual inspection. This rigorous selection process allows us to compile a statistical catalog of 561 CL-AGNs, encompassing 527 H β , 149 H α , and 129 Mg ii CL behaviors. In this sample, we find (1) a 283:278 ratio of turn-on to turn-off CL-AGNs. (2) The median Eddington ratio for CL-AGNs in the dim state is approximately λ Edd ∼ 0.01. (3) A strong correlation between the change in the luminosity of the broad emission lines (BELs) and variation in the continuum luminosity, with Mg ii and H β displaying similar responses during CL phases. (4) The Baldwin–Phillips–Terlevich diagram for CL-AGNs shows no statistical difference from the general AGN catalog. (5) Five CL-AGNs are associated with asymmetrical mid-infrared flares, possibly linked to tidal disruption events. Given the large CL-AGN sample and the stochastic sampling of spectra, we propose that some CL phenomena are inherently due to typical AGN variability during low accretion rates, particularly for CL phenomenon only occurring on one BEL. Finally, we introduce a monotonically dimming CL phase for objects characterized by a gradual decline over decades in the light curve and the complete disappearance of entire BELs in faint spectra, indicative of a real transition in the accretion disk.