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The constant gravitational pull between galaxies may change our understanding of how they die

Scientists say it is now possible to use the gravitational pull between two merging galaxies to understand why one of them stops forming stars, providing new insights into how galaxies die.

“Dead” galaxies are defined as those in which star formation has stopped, and scientists believe that death occurs in old galaxies when all their star-forming gas content is used up, or after very violent events.

But an international research team including eight universities described in a recent study published Tuesday in the Astrophysical Journal Letters a new way for galaxies to die by merging with other galaxies, forcing the expulsion of the gas that forms stars.

“Before, astronomers believed that the only way to stop galaxies from forming stars was through violent and rapid processes, such as the explosion of a massive star cluster in the galaxy to quench most of its gas and heat it up,” said Justin Spilker. , the study’s lead author and an astronomer at Texas Agricultural and Mechanical University. The rest…Our new observations show that stopping star formation does not require a ‘thunderbolt’ process. The slower fusion process can also end stars. and galaxy formation.”

The new study centers on SDSS J1448+1010, which intrigued the team because it apparently stopped forming stars about 70 million years ago, according to Dr. Spilker.

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But the aforementioned galaxy is also about to merge with another galaxy, so researchers took a closer look at the galaxy using the Hubble Space Telescope and the Atacama Large Millimeter Observatory Array, ALMA for short. an array of radio telescopes located in Chile.

What the scientists found out was a stream of material from the studied galaxy that they believe was ejected from it during the collision with the second galaxy. These streams, known as tidal tails, have been observed around other galaxies approaching each other before the merger, and are the result of the gravitational pull between the two galaxies’ massive clusters of stars and gas.

But in the case of SDSS J1448 + 1010, the gravitational pull seems to have been so violent that almost all the galactic stock needed for future star formation was expelled, with the amount of gas greater than the mass of 10 billion suns.

Dr. Spilker said: “Our observations using ALMA and the Hubble telescope prove that the real reason why the galaxy stopped forming stars is that the fusion process released about half of the gas needed for star formation into space. is between the two galaxies… Without the gas, the galaxy would not be able to continue forming stars.

While the discovery hints at the possibility of a new way for galaxies to die, it is only an observation, and it is not yet clear whether the extinction of star formation due to galactic mergers is a common occurrence in the universe, or is a one-off event. limited to the galaxy in question.

David Seton, a University of Pittsburgh graduate student in astronomy and said: “In this galactic void merger system, it is very clear that the cold gas can eventually be ejected very far … the ejection of the cold gas is a new part.” a co-author of the study. It’s an interesting galactic fading puzzle, and we’re excited to try to find more examples of it.”

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