New data obtained by NASA’s James Webb Space Telescope has revealed that one of the most ancient dead galaxies in the universe was “choked” by a supermassive black hole.
Typically, a supermassive black hole would tear a galaxy apart. In this case, the galaxy appears to have been starved of the gases and other material it receives that give rise to star formation, making the discovery highly unusual.
Combining data from the James Webb Space Telescope with additional observations from the Atacama Large Millimeter Array (ALMA), the University of Cambridge-led researchers reported their discovery in a recent paper published in Nature Astronomy.
James Webb Space Telescope
The data collected by Webb and ALMA originate from the ancient universe, just three billion years after the Big Bang. First studied by astronomer Pablo G. Pérez-González, the galaxy GS-10578, nicknamed “Pablo’s Galaxy,” is relatively small at roughly 200 billion solar masses, compared with the Milky Way’s 1.5 trillion, and its primary star-forming period occurred 12.5 to 11.5 billion years ago.
Notably, the galaxy appears to have ceased star formation at an unusually young age, as its supply of cold gas was depleted prematurely. The mechanism for this can be traced back to the galaxy’s central supermassive black hole. As the black hole repeatedly heated the gas both inside and surrounding the galaxy, it prevented new gas from entering the galaxy, thereby choking off the supply of star-forming material.
After seven hours of observations with ALMA, the astronomers were surprised to find no carbon monoxide present in Pablo’s Galaxy, signaling that the cold hydrogen gas crucial to star formation is also absent.
An Unexpected End
“What surprised us was how much you can learn by not seeing something,” said co-first author Dr Jan Scholtz from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology. “Even with one of ALMA’s deepest observations of this kind of galaxy, there was essentially no cold gas left. It points to a slow starvation rather than a single dramatic death blow.”
Spectroscopic data from Webb revealed additional anomalous behavior in the galaxy. The equivalent of sixty solar masses in neutral gas escapes GS-10578 every year, driven by a 400-kilometer-per-second cosmic wind that escapes the nearby supermassive black hole. In a typical galaxy, star fuel would last a billion years, but in GS-10578, such conditions would deplete it in as little as 16 million years, up to as much as 220 million years.
“The galaxy looks like a calm, rotating disc,” said co-first author Dr Francesco D’Eugenio, who is also affiliated with the Kavli Institute for Cosmology. “That tells us it didn’t suffer a major, disruptive merger with another galaxy. Yet it stopped forming stars 400 million years ago, while the black hole is yet again active. So the current black hole activity and the outburst of gas we observed didn’t cause the shutdown; instead, repeated episodes likely kept the fuel from coming back.”
Reconstructing the Past With the James Webb Space Telescope
The Cambridge team used the James Webb Space Telescope and ALMA data to reconstruct GS-10578’s star formation history. They found that the supermassive black hole’s actions repeated on multiple cycles, in which its wind heated or pushed out so much gas that the galaxy was unable to replenish its supply of star formation fuel.
“You don’t need a single cataclysm to stop a galaxy [from] forming stars, just keep the fresh fuel from coming in,” said Scholtz.
While this galaxy defies expectations, it also provides new context for what astronomers are seeing from new observations of the ancient universe made possible by tools such as Webb. Incoming data is displaying a growing number of galaxies that appear too old to exist as early in the universe’s history as they do.
“Before Webb, these were unheard of,” Scholtz concluded. “Now we know they’re more common than we thought – and this starvation effect may be why they live fast and die young.”
The team plans to continue their investigation, checking whether these slow choking events may have been much more common in the early universe than previously supposed. To do so, they have already been awarded an additional 6.5 hours on the James Webb Space Telescope to follow up on their previous observations.
The paper, “Measurement of the Gas Consumption History of a Massive Quiescent Galaxy,” appeared in Nature Astronomy on January 12, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.