Naud, Marie-EveArtigau, EtienneDoyon, RMalo, LisonGagne, JonathanLafreniere, DavidWolf, ChristianMagnier, Eugene A2021-09-070004-6256http://hdl.handle.net/1885/247416We present the results of a direct imaging survey for very large separation (>100 au), low-mass companions around 95 nearby young K5–L5 stars and brown dwarfs. They are high-likelihood candidates or confirmed members of the young (150 Myr) β Pictoris and AB Doradus moving groups (ABDMG) and the TW Hya, Tucana–Horologium, Columba, Carina, and Argus associations. Images in i¢ and z¢ filters were obtained with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to search for companions down to an apparent magnitude of z¢ ∼ 22–24 at separations 20″ from the targets and in the remainder of the wide 5 5 × 5 5 GMOS field of view. This allowed us to probe the most distant region where planetary-mass companions could be gravitationally bound to the targets. This region was left largely unstudied by past high-contrast imaging surveys, which probed much closer-in separations. This survey led to the discovery of a planetary-mass (9–13 MJup) companion at 2000 au from the M3V star GU Psc, a highly probable member of ABDMG. No other substellar companions were identified. These results allowed us to constrain the frequency of distant planetary-mass companions (5–13 MJup) to 0.84 0.66 6.73-+% (95% confidence) at semimajor axes between 500 and 5000 au around young K5–L5 stars and brown dwarfs. This is consistent with other studies suggesting that gravitationally bound planetary-mass companions at wide separations from low-mass stars are relatively rare.SkyMapper data products were used. The national facility capability for SkyMapper has been funded through ARC LIEF grant LE130100104 from the Australian Research Council, awarded to the University of Sydney, the Australian National University, Swinburne University of Technology, the University of Queensland, the University of Western Australia, the University of Melbourne, Curtin University of Technology, Monash University, and the Australian Astronomical Observatoryapplication/pdfen-AU© 2017. The American Astronomical Societyplanets and satellites: detectionplanets and satellites: gaseous planetsstars: individual (GU Psc)stars: low-mass201710.3847/1538-3881/aa826b2020-11-23