The Close AGN Reference Survey (CARS). Discovery of a global [CII] 158 $\mu$m line excess in AGN HE1353-1917

The [CII]158$\mu$m line is one of the strongest far-infrared (FIR) lines and an important coolant in the interstellar medium of galaxies that is accessible out to high redshifts. The excitation of [CII] is complex and can best be studied in detail at low redshifts. Here we report the discovery of the highest global [CII] excess with respect to the FIR luminosity in the nearby AGN host galaxy HE1353-1917. This galaxy is exceptional among a sample of five targets because the AGN ionization cone and radio jet directly intercept the cold galactic disk. As a consequence, a massive multiphase gas outflow on kiloparsec scales is embedded in an extended narrow-line region. Because HE1353-1917 is distinguished by these special properties from our four bright AGN, we propose that a global [CII] excess in AGN host galaxies could be a direct signature of a multiphase AGN-driven outflow with a high mass-loading factor.