Astronomers at the University of Cambridge have identified one of the oldest known dead galaxies, shedding new light on how some giant galaxies in the young Universe suddenly stop forming stars.
Using observations from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter Array (ALMA), researchers have discovered that growing supermassive black holes can slowly starve galaxies rather than completely destroying them.
Giant galaxy in the early universe
Classified as GS-10578 and nicknamed Pablo’s Galaxy, this galaxy existed just 3 billion years after the Big Bang.
Despite being so early in the history of the universe, it is huge, about 200 billion times the mass of the Sun. Most of its stars formed between 12.5 billion and 11.5 billion years ago, indicating that rapid star formation occurred before the galaxy suddenly ceased to be active.
Pablo’s galaxy, known as the “live fast, die young” galaxy, stopped producing stars while it was still relatively young. The cause appears to be a severe shortage of cold gas, which is essential for star formation.
Starvation, not destruction
Researchers found evidence of gradual suppression rather than a single catastrophic event. The supermassive black hole at the center of a galaxy repeatedly heats the surrounding gas, preventing it from replenishing the galaxy.
Over time, this process effectively suffocated star formation. The research team described this phenomenon as “death by a thousand cuts.”
ALMA’s observations were aimed at detecting carbon monoxide, a tracer of cold hydrogen gas, but after about seven hours of observation, astronomers detected almost nothing.
The lack of gas itself provided an important insight, demonstrating that the galaxy’s cessation was caused by slow starvation rather than a violent explosion.
JWST spectroscopy also revealed a powerful wind of neutral gas flowing out of the black hole at 400 kilometers per second.
These outflows remove about 60 solar masses of gas per year, potentially depleting the galaxy’s remaining fuel in just 16 million to 220 million years, much faster than the billion-year timescale typical for other galaxies.
A gentle but dangerous process
Despite these extreme conditions, Pablo’s Galaxy maintains a gently rotating disk structure, indicating that it avoids large-scale mergers and destructive collisions.
Star formation ended about 400 million years ago and began long before current black hole activity began. This pattern suggests that repeated cycles of heating and outgassing, rather than a single dramatic event, prevented new fuel from entering the galaxy.
By reconstructing the galaxy’s star formation history, the researchers concluded that the system evolved with a net zero inflow, meaning that new gas never refilled the galaxy. Repeated interventions by black holes effectively prevented galaxies from regenerating star-forming material.
Influence on early galaxy evolution
The discovery of this dead galaxy helps explain the unexpectedly increasing number of mature, giant galaxies detected by JWST in the early universe.
These galaxies appeared to be older and more evolved than models predicted, puzzling astronomers. Slow starvation by supermassive black holes now offers a convincing explanation for their rapid aging.
This study also highlights the power of combining ALMA’s ultra-deep radio observations with JWST’s infrared spectroscopy.
By analyzing both cold and warm gas, astronomers can get a more complete picture of how black holes influence the evolution of galaxies.
Future observations
The Cambridge team secured an additional 6.5 hours of JWST observation time using MIRI instruments.
These new measurements focus on warmer hydrogen gas and help scientists understand exactly how supermassive black holes starve galaxies like Pablo.
By studying more early dead galaxies, the researchers hope to reveal whether slow starvation was the primary mechanism that halted star formation throughout the early Universe.
Source link
