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06-2022

Dying early universe galaxies may be killed by their supermassive black holes

Speaking of galaxies, the Milky Way galaxy is not very active. Every year, it produces new stars worth about three to four Suns throughout the entirety of its spiral body, and stars of all ages can be found scattered throughout.

But some galaxies are even cooler – elliptical galaxies, for which most star formation stopped long ago. In these galaxies, no or very few stars younger than a certain age can be found, suggesting that at some point most star formation suddenly stopped, causing the galaxy to gradually fade out of epochs. Star to star.

Exactly how star formation stops in these smooth, almost featureless galaxies is a mystery, but astronomers think it has something to do with the supermassive black hole found at the center of every galaxy. Is. Now an international team of astronomers led by Kei Ito of Sokendai, the Graduate University for Advanced Studies in Japan, has looked back to the early universe to find out whether this is so.

Using some of the world’s most powerful telescopes, they have collected data across multiple wavelengths of light to identify galaxies whose light has traveled 9.5 billion to 12.5 billion years across the bay of space-time — Ancient galaxies like those elliptical galaxies close to us in space and time for which star formation is on the verge of extinction.

The first step was to use optical and infrared data to identify galaxies for which star formation is ongoing, and in which star formation has stopped.

The next step was to use X-ray and radio data to identify supermassive black hole activity. This is the mechanism by which astronomers believe star formation may have been extinguished. When a supermassive black hole is activated, it consumes a huge amount of matter from the space around it. The process is a messy, violent process, known collectively as “feedback”.

We all know that nothing can come out beyond a black hole’s event horizon, but the space around it is a different matter. The material revolves around the black hole, like water rounding a creek; Gravity and friction generate intense radiation that blazes across the universe.

Another form of reaction takes the form of jets blasting from the black hole’s polar regions. Material outside the event horizon is accelerated along the black hole’s external magnetic field, launching from the poles as powerful, focused jets of plasma that travel at a significant percentage of the speed of light.

Finally, active supermassive black holes generate intense winds that blow away their galaxies. All three forms of the reaction – radiation, jets and winds – are thought to heat up and push away the cold molecular gas needed to form the baby stars.

Across such vast distances, galaxies are very difficult to see; They are too small and too faint from our point of view in the here and now. So the researchers had to ‘stack’ the galaxies together to emphasize the radio and X-ray light that are telltale signs of an active supermassive black hole all those billions of years ago.

But it worked; The team found an “extra” X-ray and radio signal strong enough to be explained by lone stars in galaxies that have few or no stars. The best explanation for this signal is an active supermassive black hole. Furthermore, the signal was not as pronounced in galaxies with ongoing star formation.

This suggests, the researchers conclude, that it is highly plausible that an active supermassive black hole plays a role in the sudden deaths of these mysterious, ghostly galaxies.

Future research, he said, could help shed light on the detailed physics of this mysterious process.

research has been published in The Astrophysical Journal,

cover image credit: NASA, ESA, and the Hubble Heritage Team/STScI/AURA; J Blakeslee / Washington State University.

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