Astronomers have utilized the NASA/ESA James Webb Space Telescope to validate that supermassive black holes can deplete their host galaxies of the necessary materials to generate new stars.
Astronomers have utilized the NASA/ESA James Webb Space Telescope to validate that supermassive black holes can deplete their host galaxies of the necessary materials to generate new stars.
An international research team, co-directed by the University of Cambridge, examined a galaxy comparable to the Milky Way in the early universe, roughly two billion years following the Big Bang. Like many large galaxies, there is a supermassive black hole at its core. However, this particular galaxy is essentially ‘inactive’: it has significantly reduced its rate of star formation.
“Prior observations indicated that this galaxy was in a ‘quenched’ state: it hardly forms stars relative to its size, and we thought there might be a connection between the black hole and the cessation of star formation,” explained co-lead author Dr. Francesco D’Eugenio from Cambridge’s Kavli Institute for Cosmology. “But until Webb, we were unable to thoroughly analyze this galaxy to verify that connection or determine whether this quenched state is temporary or permanent.”
This galaxy, officially designated GS-10578 but informally referred to as ‘Pablo’s Galaxy’ after the colleague who chose to study it in depth, is remarkably large for such an early epoch in the universe: it has a total mass around 200 billion times that of our Sun, with most of its stars having formed between 12.5 and 11.5 billion years ago.
“In the early universe, most galaxies are rapidly forming stars, making it fascinating to observe such a substantial dormant galaxy during this timeframe,” remarked co-author Professor Roberto Maiolino, also from the Kavli Institute for Cosmology. “Given its significant size, whatever halted star formation must have occurred relatively quickly.”
Using Webb, the scientists observed that this galaxy is ejecting vast quantities of gas at velocities reaching approximately 1,000 kilometers per second, sufficient to escape its gravitational influence. These rapid outflows are propelled outward by the black hole.
Similar to other galaxies with active black holes, ‘Pablo’s Galaxy’ exhibits swift outflows of hot gas; however, these gas clouds are sparse and possess minimal mass. Webb identified a new component of the wind that previous telescopes couldn’t detect. This gas is cooler, meaning it is denser and, importantly, does not emit light. Thanks to Webb’s enhanced sensitivity, it can observe these dark gas clouds, as they obstruct some light from the galaxy situated behind them.
The amount of gas being expelled from the galaxy exceeds what would be necessary for ongoing star formation. Essentially, the black hole is leading the galaxy to its demise by depriving it of the vital ‘fuel’ needed for new stars to form. The findings are published in the journal Nature Astronomy.
“We have identified the cause,” stated D’Eugenio. “The black hole is effectively extinguishing this galaxy and maintaining its dormant state by cutting off the ‘food’ it requires to generate new stars.”
While previous theoretical frameworks suggested that black holes influence galaxies in this manner, it had not been possible to observe such an impact directly before Webb.
Earlier theories proposed that the cessation of star formation has a chaotic and destructive effect on galaxies, altering their structure. However, the stars within this disc-shaped galaxy continue to move in an organized manner, indicating that this isn’t always the case.
“We have known that black holes significantly affect galaxies, and it may be common for them to halt star formation, but it was only with Webb that we could directly confirm this,” remarked Maiolino. “This highlights another way in which Webb represents a significant advancement in our capacity to investigate the early universe and its evolution.”
Further observations with the Atacama Large Millimeter-Submillimeter Array (ALMA), focusing on the coldest and darkest gas components of the galaxy, will provide additional insights into whether and where any potential fuel for star formation remains hidden in this galaxy, as well as the influence of the supermassive black hole in the area surrounding the galaxy.
This research was partly funded by the Royal Society, the European Union, the European Research Council, and the Science and Technology Facilities Council (STFC), which is a part of UK Research and Innovation (UKRI).
