Evolution of an unusual monster galaxy

Astronomers have discovered an unusual monster galaxy that existed about 12 billion years ago.

Using the WM Keck Observatory in Hawaii, an international team led by the University of California, Riverside (UCR) found that XMM-2599 formed stars at a high rate and then died. Just why is still unclear.

“Even before the Universe was two billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultra-massive galaxy,” says Benjamin Forrest, lead author of a paper in The Astrophysical Journal Letters.

“More remarkably, we show that XMM-2599 formed most of its stars in a huge frenzy when the Universe was less than 1 billion years old, and then became inactive by the time the Universe was only 1.8 billion years old.”

The team found that XMM-2599 formed more than 1000 solar masses a year in stars at its peak of activity. In contrast, the Milky Way forms about one new star a year.

“We have caught XMM-2599 in its inactive phase,” says UCR co-author Gillian Wilson. 

“We do not know what it will turn into by the present day. We know it cannot lose mass. An interesting question is what happens around it. As time goes by, could it gravitationally attract nearby star-forming galaxies and become a bright city of galaxies?”

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