Gemini Imaging of the Host Galaxies of Changing-Look Quasars
  Changing-look quasars are a newly-discovered class of luminous active
galactic nuclei that undergo rapid ($\lesssim$10 year) transitions between Type
1 and Type 1.9/2, with an associated change in their continuum emission. We
characterize the host galaxies of four faded changing-look quasars using
broadband optical imaging. We use \textit{gri} images obtained with the Gemini
Multi Object Spectrograph (GMOS) on Gemini North to characterize the surface
brightness profiles of the quasar hosts and search for [O III]
$\lambda4959,\lambda5007$ emission from spatially extended regions, or
voorwerpjes, with the goal of using them to examine past luminosity history.
Although we do not detect, voorwerpjes surrounding the four quasar host
galaxies, we take advantage of the dim nuclear emission to characterize the
colors and morphologies of the host galaxies. Three of the four galaxies show
morphological evidence of merger activity or tidal features in their residuals.
The three galaxies which are not highly distorted are fit with a single
S\'ersic profile to characterize their overall surface brightness profiles. The
single-S\'ersic fits give intermediate S\'ersic indices between the $n=1$ of
disk galaxies and the $n=4$ of ellipticals. On a color-magnitude diagram, our
changing-look quasar host galaxies reside in the blue cloud, with other AGN
host galaxies and star-forming galaxies. On a color-S\'ersic index diagram the
changing-look quasar hosts reside with other AGN hosts in the "green valley".
Our analysis suggests that the hosts of changing-look quasars are predominantly
disrupted or merging galaxies that resemble AGN hosts, rather than inactive
galaxies.
