Astronomers have observed the effect of a distant feeding black hole spewing enormous amounts of energy and blowing huge cosmic bubbles into the surrounding material. Observations of the galaxy cluster MS0735, located 2.6 billion light-years away, could reveal new information about the mysterious voids or “radio bubbles” that surround the black hole and why it doesn’t simply collapse like a deflated balloon under the pressure of its surroundings.
Lead author of the study and McGill University physicist Jack Orlowski-Scherer said “We are looking at one of the most powerful explosions ever observed from a supermassive black hole, This is what happens when you feed a black hole and it violently ejects a huge amount of energy.”
These home galaxies and their supermassive black hole inhabitants are often found together in groups of hundreds or even thousands, groupings called galaxy clusters. These clusters are also home to atmospheres that fill the space between galaxies with incredibly hot gas or plasma at temperatures of up to 90 million degrees Fahrenheit (50 million degrees Celsius). Although this plasma can cool over time, allowing cold dense gas to form and eventually collapse to give birth to new stars, black hole power can work against this process.
Supermassive black holes can reheat this gas through violent ejections of material. These ejections occur when some of this matter is not absorbed by the black hole, but is instead pulled toward its poles, from where it is shot out at near the speed of light. This process, known as “feedback”, quenches the formation of new stars, with jets of material also carving out cavities in the surrounding gas.
As this gas is expelled from the center of galaxy clusters, it is replaced by bubbles that emit radio waves. Moving these huge volumes of gas, in turn, requires enormous amounts of energy, and in addition to discovering what remains in these evacuated cavities, astronomers have struggled to understand where that energy comes from.
To learn more about such gas bubbles in galaxy clusters and the processes that create them, a team of astronomers including Orlowski-Scherer trained the Green Bank Telescope’s MUSTANG-2 receiver on the MS0735 cluster. The observations from the Green Bank Telescope were supplemented by X-ray data collected earlier from MS0735 by NASA’s Chandra X-ray Observatory.
They also used the subtle warping effect that fast-moving electrons in the cluster’s hot gas have on the cosmic microwave background (CMB), a field of radiation left over from an event shortly after the big bang that uniformly fills the universe.
This effect on this fossil radiation, which was emitted 380,000 years after the beginning of the universe, when the universe expanded and cooled enough to allow electrons to bind with protons, creating the first atoms, thereby allowing photons to travel freely and create “the first light ” is called the Sunyaev-Zeldovich (SZ) effect.
MUSTANG-2 makes its observations at 90 GHz, which is the frequency at which the SZ effect signal is mainly thermal pressure.
research associate and European Southern Observatory (ESO) astronomer Tony Mroczkowsk said “With the power of MUSTANG-2, we are able to see into these cavities and begin to determine exactly what fills them and why they don’t collapse under pressure”.
The team found that at least some of the support that prevents cavities from collapsing comes from things other than heat, and those non-thermal sources include particles moving at speeds close to the speed of light, high-speed charged particles called cosmic rays, and turbulence. They also found that a small contribution comes from magnetic fields.
This means that mixing thermal and non-thermal sources makes the pressure boost in radio bubbles around supermassive black holes more subtle than previously thought. A team of astronomers is now focusing on observing the same system at different frequencies of electromagnetic radiation to see how exotic the black hole outflow is and to gain deeper insight into the physics of galaxy clusters.
“These new discoveries are the deepest high-fidelity imaging to date of the NW thermodynamic state of cavities in a galaxy cluster,” added research co-author and U.S. astronomer Tracy Clarke Naval Research Laboratory. “We knew this was an exciting system when we studied the radio core and lobes at low frequencies, but we are only now beginning to see the full picture.
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