An international research team using the JWST has found 'photographic evidence' that brings astronomers a step closer to solving a longstanding mystery about black holes
Study: JWST Reveals How Black Holes are Fed: Kiloparsec-scale Multiphase Filaments Feed Subkiloparsec Circumnuclear Disks (DOI: 10.3847/2041-8213/ae81ae)
An international research team, including an astronomer from the University of Michigan, have revealed how certain black holes manage to eat and grow while simultaneously flinging their food across galaxies.
"We've found this almost smoking-gun, photographic evidence of how the black holes get their fuel, how they're getting this material to enlarge themselves," said Hyunseop "Joseph" Choi, postdoctoral researcher in the University of Michigan's Department of Astronomy.
The research behind the discovery was led by the University of Montreal and enabled by the world's most powerful space telescope, the JWST. For this study, the JWST, a NASA mission developed in partnership with the Canadian Space Agency and the European Space Agency, observed a galaxy named NGC 4696 with a supermassive black hole at its center.
"We're finally seeing how gas falls back into a black hole for the first time with the state-of-the-art JWST observatory," said Choi, who began working on this project as a postdoctoral fellow at Montreal before joining Michigan.
Nearly every massive galaxy in the universe has a supermassive black hole at its core, millions or even billions of times more massive than the sun. When these black holes are actively pulling in surrounding material, they switch on like cosmic engines. They unleash powerful jets and winds of energy outward that can sculpt the entire galaxy around them, slowing down the birth of new stars and influencing how the galaxy grows over time. Astronomers call these types of black holes active galactic nuclei, or AGN.
Despite extensive research, a puzzle has stumped scientists for years. If an AGN's jets heat up the surrounding gas, that should, in principle, shut off the black hole's food supply. So how does it keep feeding and growing?
The leading hypothesis is that the gas eventually cools back down, condenses into long thin streamers called filaments, and falls back toward the galaxy's center. The black hole thus feeds the process that then feeds the black hole. Despite decades of searching, directly observing how these filaments actually connect to the black hole has remained very difficult. That connection, a sort of missing link, is exactly what this new study reveals.
"What JWST is revealing is that black holes may be the ultimate cosmic recyclers," said Julie Hlavacek-Larrondo, a professor at the University of Montreal and lead author of the team's new study published in The Astrophysical Journal Letters.
"They release enormous amounts of energy that heat their surroundings, yet that same gas can later cool into thin filaments that fall back inward and feed the black hole again. We are finally seeing this self-sustaining cycle in action."
To test whether this explanation holds up, the team also ran computer simulations of the system. The simulated gas behaved in a way that closely matched what JWST observed, lending strong independent support to the proposed picture.
"It is exciting that JWST observations now allow us to directly test and constrain our simulations of black hole feeding, by comparing them to what we are seeing around a real black hole," said Minghao Guo, a doctoral student at Princeton University and co-author who led the simulations featured in the study.
A similar disk structure had previously been seen in another galaxy, NGC 1275 in the Perseus Cluster, using the ALMA Observatory. These new results in NGC 4696 suggest that this recycling mechanism may be common to massive galaxies across the universe.
"We've found just one example, so we're hoping to use JWST in the near future to see whether we can capture this kind of image from other black holes," Choi said. "I am very much looking forward to what our future JWST programs may reveal about how black holes feed themselves."
