First observation of a distant galaxy in the process of “dying”

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Paris | Astronomers were able to observe for the first time a distant galaxy “dying” after losing about half of the gas used to make stars, according to a study released Monday.

Data collected by the Alma telescope at the European Southern Observatory (ESO) in Chile suggests that this phenomenon, usually attributed to the effect of a black hole, is the result here of the collision of this galaxy with a other.

‘ID2299’ is so distant that its light has taken 9 billion years to reach us. It is observed when the Universe was only 4.5 billion years old. “

This elliptical-shaped galaxy “is going through a rather extreme phenomenon, never observed at such a distance,” Emanuele Daddi, astrophysicist at the Saclay Nuclear Research Center (which depends on the CEA), told AFP. author of the study published in Nature Astronomy and conducted by Annagrazia Puglizi, of the British University of Durham.

ID2299 “is expelling more than half of its gas, its fuel for star formation”, at a phenomenal rate, equivalent to the mass of 10,000 suns per year, he explained. And this while continuing to consume this same gas to produce stars at a very high rate, with a mass equivalent to about 550 times our sun. By comparison, our galaxy, the Milky Way, produces the equivalent of three per year.

Under these conditions, the galaxy should become sterile in a few tens of millions of years, in no time at the cosmic scale.

The study recalls that so far such a gas “leak” has been explained by the effect of winds caused by star formation or the activity of a supermassive black hole located in the galactic nucleus.

But “we have been able to show that another mechanism is at work, with a collision of galaxies (…) which has already taken place”, according to Mr. Daddi.

For Chiara Circosta, co-author of the study and researcher at University College London, quoted in a press release from the European Southern Observatory (ESO), the observation carried out with Alma “sheds new light on the mechanisms stopping training. stars in distant galaxies ”.

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