Galaxy Evolution in the Post-Merger Regime with UNIONS – Leonardo Ferreira (FURG)

Galaxy mergers can strongly transform galaxies, but their impact depends critically on time since coalescence. Using UNIONS imaging and the MUMMI deep-learning framework, we identify large samples of galaxy mergers and assign post-merger timescales, allowing merger-driven evolution to be studied as a sequence rather than as a single population. With this framework, we track the temporal evolution of star-formation enhancement, quenching, AGN activity, and stellar mass assembly in post-merger galaxies.

The main focus of this talk will be the first results from the Galaxy Evolution in the Post-Merger Regime series. We find that star formation is strongly enhanced after coalescence, reaching nearly a factor of two above matched control galaxies and remaining elevated for several hundred Myr. This merger-driven activity contributes significantly to stellar mass growth, with the post-merger phase adding more stellar mass than the pre-coalescence pair phase. The enhancement then declines, returning to normal levels after roughly 1 Gyr. I will also briefly place these results in the broader post-merger sequence: post-starburst and rapidly quenched systems become more common within the first few hundred Myr, AGN activity peaks shortly after coalescence, and the stellar mass excess associated with mergers extends over kiloparsec scales rather than being confined only to the nucleus.

Together, these results provide a time-resolved observational picture of how mergers drive star formation, black hole growth, quenching, and structural transformation in galaxies.

YouTube Link: https://youtu.be/QWbsLZ4x97M