Supermassive black holes can slow star formation not only in their own galaxies but also in nearby galaxies, suggesting that they may have played a much larger role in shaping the evolution of galaxies in the early universe than previously thought.
The powerful radiation emitted by active supermassive black holes, which are thought to exist at the centers of most galaxies, can slow the growth of stars not only in their host galaxies, but also in galaxies millions of light-years away, a new study has found.
“Traditionally, people have thought that galaxies evolve largely on their own because they are so far apart,” explains Yonda Zhu, a postdoctoral researcher at the University of Arizona’s Department of Astronomy and Steward Observatory, who led the study.
“But we found that a highly active supermassive black hole in one galaxy can influence other galaxies millions of light-years away, suggesting that galaxy evolution may be a rather collective effort.”
Destructive properties of supermassive black holes affect star growth
Zhu explained that this is known as the “galactic ecosystem” and can be compared to the intertwined ecosystems on Earth.
“An active supermassive black hole is like a hungry predator that dominates an ecosystem,” he says. “Simply put, it swallows matter and affects how stars in nearby galaxies grow.”
Since they were first predicted in the early 1900s, the destructive and eerie properties of black holes have fascinated scientists and the general public alike.
Black holes, considered the most extreme objects in the universe, contain enormous mass and gravity, and can capture nearby matter and even light if they get too close.
A small subset of the Milky Way galaxy, including its central black hole, is known as “supermassive” and has millions, and sometimes billions, times the mass of the Sun.
Super energy emitters devour all surrounding matter
As the name suggests, black holes are invisible. But when a supermassive black hole actively eats up the material around it, it appears as a very bright spot in telescope images, sometimes emitting hundreds of trillions of times more energy than the sun.
Astronomers call these cosmic monsters quasars. This is the stage in a black hole’s life when it forms a swirling disk of gas and dust that spirals inward, emitting enormous amounts of energy, often more than the energy of its entire host galaxy.
solve a long-standing mystery
Early observations by the James Webb Space Telescope suggested that there were few galaxies around giant quasars in the early universe. This result was surprising because large galaxies are typically found in dense star clusters rather than in isolation.
“We thought JWST could be broken,” Zhu said. “We then realized that galaxies might actually exist, but they were difficult to detect because very recent star formation had been suppressed.”
That realization led to bold new ideas. Could these extremely bright, supermassive black holes not only affect their own galaxies, but also inhibit star formation in neighboring galaxies?
Intense heat breaks down molecular hydrogen that helps star formation
To test this idea, the research team studied J0100+2802, one of the brightest quasars ever observed. J0100+2802 is powered by a supermassive black hole about 12 billion times the mass of the Sun.
A team of scientists used JWST to measure the emission of O III, an ionized form of oxygen, a specific gas that tracks very recent star formation in galaxies. The low O III ratio implies that ideal star-forming conditions in large clouds of cold gas are broken down.
The research team observed distinct differences between galaxies within a million light-year radius of the dominant quasar. The galaxy exhibits weak O III emission compared to ultraviolet light, consistent with suppressed and very recent star formation.
“Black holes are known to ‘eat’ a lot of things, but in the process of active eating and in the form of bright quasars, they also emit very strong radiation,” Zhu said. “The intense heat and radiation split the hydrogen molecules that make up the vast interstellar gas cloud, eliminating any chance of it accumulating and turning into new stars.”
Testing phenomena across multiple quasar fields
The researchers hope to test whether this phenomenon extends to multiple quasar regions and understand exactly how galaxies are affected by neighboring quasars, and whether other less obvious factors are at play.
Zhu concludes: “Understanding how galaxies interacted with each other in the early universe helps us better understand how our galaxy formed.
“We now know that supermassive black holes may have played a much larger role in the evolution of galaxies than once thought, acting as cosmic predators and influencing the growth of stars in nearby galaxies in the early universe.”
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