How a Supermassive Black Hole Silently Killed an Ancient Galaxy

Astronomers have discovered how a massive galaxy, known as Pablo's Galaxy, died just three billion years after the Big Bang. The findings reveal that its star formation stopped not from a sudden explosion but from a slow starvation caused by its own supermassive black hole. The discovery, made using ALMA and JWST observations, shows that powerful winds from the black hole stripped away the cold gas needed to form new stars. This process helps explain why many early galaxies appear unexpectedly mature in recent JWST images. Pablo's Galaxy, officially named GS-10578, weighs around 200 billion times the mass of the Sun. Its active star-forming phase ended roughly 400 million years ago, far earlier than expected. Instead of a violent event, ALMA detected almost no cold gas left in the galaxy, confirming that it had been starved of fuel over time. JWST spectroscopy revealed neutral gas winds blasting out from the black hole at 400 kilometres per second. These winds removed about 60 solar masses of gas each year, preventing fresh material from reaching the galaxy. The black hole's repeated heating cycles had already expelled most of the cold gas long before the current outflows began. The Cambridge-led research team now plans further JWST observations to study warmer hydrogen gas in similar galaxies. Their goal is to understand how supermassive black holes systematically cut off star formation by depriving galaxies of the raw materials they need. This study highlights the importance of combining ALMA's deep radio imaging with JWST's infrared capabilities. Together, they provide a clearer picture of how black holes shape the evolution of galaxies in the early Universe. The death of Pablo's Galaxy shows that supermassive black holes can strangle star formation by slowly removing cold gas. This process explains the growing number of massive, mature galaxies seen by JWST in the early Universe. With additional JWST time secured, researchers will continue investigating how black holes influence galaxy growth. The findings reinforce the need for multi-wavelength observations to unravel the complex relationship between black holes and their host galaxies.