Astronomers are closer to solving the mystery of how supermassive black holes feed themselves thanks to new images from the James Webb Space Telescope, or JWST.
The images provide the clearest view ever seen of gaseous filaments connecting a galaxy's hot atmosphere to the rotating disk of gas that feeds its central supermassive black hole.
Michigan State University helped an international team, led by the Université de Montréal, perform the observations and interpret the data, finding answers to a question that has stumped scientists for decades. The results were reported in the July 14 issue of The Astrophysical Journal Letters.
"JWST observations are offering us thousands of new facts and measurements, and I can report it's a lot to absorb," said Megan Donahue, MSU University Distinguished Professor of physics and astronomy. "We are all working together to solve the astrophysics questions about how these black holes get their fuel and how they interact with their host galaxy."
Self-regulating black holes
Nearly every large galaxy in the universe has a supermassive black hole, or SMBH, at its center 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, blasting powerful jets 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.
But if an AGN's jets heat up the surrounding gas, it 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 in a self-regulating process.
To test this hypothesis, the team pointed JWST at galaxy NGC 4696, the central galaxy of the Centaurus Cluster, a dense group of galaxies located about 145 million light-years from Earth and one of the best laboratories for studying AGN mechanisms.
With nearly eight hours of observing time using JWST's NIRSpec instrument, the team produced detailed maps of the gas's motion deep inside the black hole's sphere of influence, at a resolution sharp enough to pick out features roughly 30 light-years — a tiny slice of a galaxy hundreds of thousands of light-years wide.
These maps showed that the S-shaped swirl is actually a spinning disk of gas wrapped around the SMBH, nearly 800 light-years across, with material whipping around at up to 600 kilometers per second. And critically, that disk appears physically connected to one of the large infalling filaments stretching outward into the galaxy. The observations showed gas flowing along the filament and pouring into the disk that feeds the SMBH.
Closing the loop
The study helps astronomers paint a better picture of the full feeding cycle of a SMBH. Jets from the black hole pump energy into the galaxy's surrounding gas. That gas eventually cools, becomes unstable, and collapses into long filaments, some only a few hundred light-years wide but stretching thousands of light-years long. Magnetic forces slow the gas's rotation as it falls, steering it inward. It accumulates into a spinning disk around the black hole. The disk feeds the black hole. The black hole fires its jets. And the cycle begins again.
To test whether this explanation holds up, the team also ran state-of-the-art 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's been really exciting to participate in this project," MSU Physics and Astronomy Professor Mark Voit said. "Calculations done by our Michigan State group predict that magnetic fields should help feed the universe's biggest black holes by channeling cool gas toward them, and it's amazing to see that happening in these JWST images."
