Live Fast, Die Young: The Meteoric Rise of Giant Galaxies

Galaxies are complex collections of stars, gas, and dark matter. The largest galaxies host many of the Universe’s stars and harbor the most extreme supermassive black holes. Today these massive galaxies are ancient relics – they stopped forming stars long ago and shine with a dim, reddish glow. For decades, astronomers assumed these giants formed slowly over billions of years, but until recently, we did not have the tools to directly observe their adolescence. In its first few years of operation, the James Webb Space Telescope has revolutionized our view of the early Universe, peering deeper into cosmic history than ever before. And what it revealed shocked us: massive galaxies that were already complete less than 4-5 hundred million years after the Big Bang. It’s not just that they formed early – they lived fast and died young. Even more puzzling: there are far too many of them. Our best theoretical models struggle to explain how the early Universe built so many giants so quickly, or why they stopped forming stars and retired so early. In this talk I’ll describe how my team is hunting down these cosmic overachievers and what their existence means for our understanding of how the Universe evolved.