Astronomers have used the NASA/ESA James Webb Space Telescope to confirm that a supermassive black hole may be robbing its host galaxy of the fuel it needs to form new stars. Using Webb, an international team co-led by the University of Cambridge observed a galaxy roughly the same size as the Milky Way in the early universe, about 2 billion years after the Big Bang. Like most large galaxies, at its centre is a supermassive black hole. But this galaxy is essentially “dead” – it has largely stopped forming new stars. Photo by Francesco DeEugenio
Using the NASA/ESA James Webb Space Telescope, astronomers have confirmed that supermassive black holes can rob their host galaxy of the fuel it needs to form new stars, a finding reported in the journal Nature Astronomy.
An international team co-led by the University of Cambridge used the Webb Telescope to observe a galaxy roughly the size of the Milky Way as it existed 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. But the galaxy is essentially “dead” – it has largely stopped forming new stars.
“We know from previous observations that this galaxy is in an extinct state – not many stars are forming given its size, and we expect there to be a link between the black hole and the end of star formation,” said co-lead author Dr Francesco D’Eugenio from the Kavli Institute for Cosmology at the University of Cambridge.
“But until Webb came along, we hadn’t been able to study this galaxy in enough detail to confirm its connection, or to know whether its disappearance was temporary or permanent.”
The galaxy, officially named GS-10578 but nicknamed “Pablo’s Galaxy” after the colleague who decided to observe it in detail, is massive for the early universe: Its total mass is about 200 billion times that of the Sun, and most of its stars formed between 12.5 and 11.5 billion years ago.
“In the early Universe, most galaxies are forming lots of stars, so it’s intriguing to see such a massive dead galaxy at this time,” said co-author Professor Roberto Maiorino, also of the Kavli Institute for Cosmology. “If it had enough time to grow to such a massive size, it’s likely that the process that stopped star formation happened relatively quickly.”
Using Webb, the researchers discovered that the galaxy is expelling huge amounts of gas at speeds of about 1,000 kilometers per second — fast enough to escape the galaxy’s gravity. These fast-moving winds are being “pushed” out of the galaxy by the black hole.
Like other galaxies with accreting black holes, Pablo’s Galaxy has fast-flowing winds of hot gas, but these gas clouds are thin and have very little mass. Webb detected the presence of a new wind component not seen by previous telescopes: this gas is cold, dense, and, importantly, doesn’t emit any light. With its excellent sensitivity, Webb can see this because these dark gas clouds block some of the light from the galaxy behind them.
The mass of gas being ejected from the galaxy is greater than the amount the galaxy needs to keep forming new stars. Essentially, the black hole is starving the galaxy to death.
“We’ve found the culprit,” DeEugenio said. “The black hole is killing this galaxy and keeping it dormant by cutting off the source of the ‘food’ it needs to form new stars.”
Previous theoretical models predicted that black holes have this effect on galaxies, but before Webb it had not been possible to detect this effect directly.
Previous models predicted that the end of star formation would bring intense turbulence to the galaxy, destroying its shape in the process, but the stars in this disk-like galaxy still move in an orderly fashion, suggesting that this isn’t necessarily the case.
“We knew that black holes have a profound effect on galaxies, and that it may be common for black holes to halt star formation, but until the discovery of Webb we had never been able to confirm this directly,” Maiorino said. “The discovery of Webb marks another major step forward in our ability to study the early universe and its evolution.”
New observations by the Atacama Large Millimeter/submillimeter Array (ALMA) targeting the coldest, darkest gaseous components of our Galaxy will tell us more about whether and where fuel for star formation is still hidden within our Galaxy, and what influence the supermassive black hole in the periphery of our Galaxy may have.
Further information: Rapidly rotating post-starburst galaxy annihilated by supermassive black hole feedback at Z=3, Nature Astronomy (2024). DOI: 10.1038/s41550-024-02345-1. www.nature.com/articles/s41550-024-02345-1
Provided by University of Cambridge
Source: Astronomers discover black hole is “starving” its host galaxy (September 16, 2024) Retrieved September 16, 2024 from https://phys.org/news/2024-09-astronomers-black-hole-starving-host.html
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