Black holes can cause galaxies to age prematurely

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Black holes can cause galaxies to age prematurely

Whereas many galaxies eventually run out of the gas and dust they need to make new stars, a few “die young” by ceasing star birth hundreds of millions of years earlier than models of galactic evolution suggest. Astronomers don’t yet fully understand this premature aging, but a new study suggests that having an active black hole at the center of the galaxy could be one major factor. Using radio telescopes, researchers scrutinized four elliptical galaxies apparently on the cusp of changing from groups filled with new stars to ones that had very few. These galaxies lie between 275 million and 375 million light-years from Earth. All appear to have recently shed the vast volumes of gas needed to trigger the formation of new stars, but why that happened isn’t clear, the researchers say. The gas probably wasn’t stripped away by interactions with other galaxies, because the star groups are relatively isolated in space. In the case of a galaxy dubbed J0836 (see image), a large mass of cold hydrogen gas (depicted in aqua) near the galaxy may have been blown out of its former home by a supermassive black hole at the center of the galaxy, the team reports in the Monthly Notices of the Royal Astronomical Society. That cloud lies along a path of material that radiates strongly in radio wavelengths, a sign that the cloud may have been expelled from its parent galaxy at a time when its central black hole was much more active than it is now. Further analyses of these four galaxies, and many others like them, should help pin down the possible causes of premature aging in such star groups.

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