September 16 () –
The James Webb Space Telescope has confirmed that supermassive black holes can deprive their host galaxies of the fuel they need to form new stars.
An international team, co-led by the University of Cambridgeused the Webb telescope to observe a galaxy roughly the size of the Milky Way in the early universe, about 2 billion years after the Big Bang. Like most large galaxies, it has a supermassive black hole at its center. However, this galaxy is essentially “dead”: has stopped forming new stars.
The results are published in the journal Nature Astronomy.
“Based on previous observations, we knew that this galaxy was in an extinct state: it is not forming many stars given its size, and we expect there to be a link between the black hole and the end of star formation,” he said. in a statement co-lead author Dr Francesco D’Eugenio from the Kavli Institute for Cosmology at Cambridge.
“However, until Webb, we had not been able to study this galaxy in enough detail to confirm that link, and we did not know whether this extinct state was temporary or permanent.”
PAUL’S GALAXY
This galaxy, officially named GS-10578 but nicknamed “Pablo’s Galaxy” after the colleague who decided to observe it in detail, is massive for such an early period in the universe: Its total mass is approximately 200 billion times the mass of our sun, and most of its stars formed between 12.5 and 11.5 billion years ago.
“In the early universe, most galaxies were forming lots of stars, so it’s interesting to see such a massive dead galaxy in this time period,” said co-author Professor Roberto Maiolino, also from the Kavli Institute of Cosmology. “If it had enough time to get to this massive size, whatever process stopped star formation probably happened relatively quickly.”
Using the Webb telescope, researchers detected that this galaxy is expelling large amounts of gas at speeds of about 1,000 kilometers per second, which is fast enough to escape the galaxy’s gravitational pull. These fast-moving winds are being “pushed” out of the galaxy by the black hole.
Like other galaxies with accreting black holes, the Pablo galaxy has fast outflow winds of hot gas, but these gas clouds are faint and have little mass. The Webb telescope detected the presence of a new wind component, one that could not be seen with previous telescopes. This gas is cooler, meaning it is denser and, crucially, does not emit light. The Webb telescope, with its superior sensitivity, can see these dark gas clouds. because they block part of the light from the galaxy behind them.
The mass of gas being ejected from the galaxy is greater than the galaxy would need to continue forming new stars. In essence, the black hole is starving the galaxy.
“We found the culprit,” D’Eugenio said. “The black hole is killing this galaxy and keeping it dormant, cutting off the source of ‘food’ that the galaxy needs to form new stars.”
Although previous theoretical models had predicted that black holes had this effect on galaxies, before Webb, It had not been possible to detect this effect directly.
Previous models had predicted that the end of star formation has a violent, turbulent effect on galaxies, destroying their shape in the process. But the stars in this disk-shaped galaxy are still moving in an orderly fashion, which suggests that this is not always the case.
“We knew that black holes have a massive impact on galaxies, and it may be common for them to stop star formation, but until Webb, We couldn’t confirm it directly“Maiolino said. “It’s another way in which Webb is a major step forward in terms of our ability to study the early universe and how it evolved.”
New observations with the Atacama Large Millimeter-Submillimeter Array (ALMA), targeting the galaxy’s cooler, darker gas components, will tell us more about whether and where there is still hidden fuel for star formation in this galaxy, and what is the effect of the supermassive black hole on the region surrounding the galaxy.
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