Morphology of Optical Changing-Look AGN-host Galaxies: Evidence for an Important Role of Mergers

Abstract

Optical changing-look active galactic nuclei (CL-AGNs) are characterized by the (dis)appearance of broad emission lines on unexpectedly short timescales. However, the underlying mechanisms and their potential connection to host-galaxy properties are still unclear. In this work, we present an analysis of the morphology for 63 low-redshift CL-AGNs (z < 0.15) selected from the largest CL-AGN catalog (Guo et al. 2025) to date, using images from DESI DR10 and employing both non-parametric methods and visual inspection. We find that CL-AGN hosts exhibit a concentration like late-type spirals, asymmetry like early-type spirals, and smoothness like ellipticals. This is confirmed by their Gini-M20 coefficients, suggesting weak/modest disturbances. Based upon our visual inspection, we further identify that 18 (29%) out of 63 sources are mergers, among which ~56% (10/18) show shell features. Compared to different non-CL-AGN samples, CL-AGN hosts have a higher (~2\times) possibility of being merging systems. Our results indicate that mergers/interactions may play an important role in driving the changing-look behavior.