Galaxy mergers can rapidly shut down star formation

ABSTRACT Galaxy mergers trigger both star formation and accretion on to the central supermassive black hole. As a result of subsequent energetic feedback processes, it has long been proposed that may be promptly extinguished in galaxy merger remnants. However, this prediction widespread, rapid quenching late stage recently called into question with modern simulations never tested observationally. Here we perform first empirical assessment long-predicted end phase sequence. Based sample ∼500 post-mergers identified from Ultraviolet Near Infrared Optical Northern Survey (UNIONS), show frequency post-merger galaxies have rapidly shutdown their following previous starburst is 30–60 times higher than expected control non-merging galaxies. No such excess found close pairs, demonstrating can indeed lead halt formation, but process only manifests after coalescence.