A study looking back at the universe 12.5 billion years ago revealed that some black holes stopped star formation in the galaxies they were in.
Stars are formed by the collapse and condensation of clouds of molecular hydrogen gas. Star formation is already underway in our own Milky Way and other galaxies. But in some galaxies (especially large, elliptical galaxies) star formation seems to have stopped billions of years ago.
Astronomers suspect that the powerful radiation emitted by material orbiting a supermassive black hole at the center of a galaxy could heat the molecular gas in that galaxy and inhibit star formation. Such galaxies are described as “red and dead” because once star formation ceases, all that remains is long-lived, cool red stars.
While there is a lot of indirect evidence that energy from black holes can inhibit star formation, astronomers are still awaiting final observations of this process and working to understand how this happens. Now, a research team has discovered that galaxies from the early universe that have stopped forming stars have more active supermassive black holes at their centers than those in galaxies that are still forming stars.
During the research, galaxies that existed between 9.5 and 12.5 billion years ago were looked at. X-ray and radio signals from active black holes were investigated. Since these signals were very weak, it was necessary to amplify the incoming signals by superimposing them and then averaging them. As a result of the research, it was found that red and dead galaxies have stronger black hole activity than galaxies still forming stars.
While the new findings, published in The Astrophysical Journal, do not fully prove that black holes stop star formation, they strengthen this hypothesis by linking active black holes to red and dead galaxies. Scientists think NASA’s James Webb Space Telescope, which will launch this summer, will provide more evidence.
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