New study challenges the role of galaxy mergers in star formation

The research team, led by FIU physics graduate student Camilo Casimiro, analyzed over 11,000 simulated galaxies using the IllustrisTNG cosmological framework. By tracking billions of years of cosmic evolution, the study found that galaxy mergers are neither necessary nor sufficient to stop the creation of new stars. Instead of the expected correlation between collisions and quenching, the data showed that only 3% of major mergers were followed by a halt in star formation within a billion years.

Even when accounting for smaller interactions, only 12% of cases were linked to a shutdown in activity. Most galaxies that stopped forming stars showed no evidence of a recent collision at all, pointing toward slower internal processes rather than catastrophic events. According to co-author and assistant professor Asa Bluck, the focus should shift from spectacular black hole outbursts to the total energy released by black holes over vast timescales. These findings, published in the Monthly Notices of the Royal Astronomical Society, suggest that the evolution of the universe is driven more by gradual, quiet shifts than by the dramatic pileups long favored in astrophysics.