We used to think giant galaxy car crashes killed off star-making, but it turns out that’s not what’s actually pulling the plug.
arXiv · March 16, 2026 · 2603.12651
Why it matters
A study of over 11,000 galaxies has overturned a decades-old paradigm by showing that mergers are neither necessary nor sufficient to kill a galaxy. This suggests that star formation is actually shut down by internal, 'secular' processes rather than violent cosmic crashes.
From the abstract
The cessation of star formation in galaxies, known as 'quenching', is a complex, multi-scale process which has been theorized to be linked to galaxy mergers. In this paper, we investigate the potential role of mergers in quenching galaxies in the IllustrisTNG cosmological hydrodynamical simulation. We track the evolution of over 11,000 central galaxies in the simulation with stellar mass $M_\star \ge 10^9 M_\odot$ at $z = 0$ throughout the entirety of cosmic history. We compare their star format