Largest Galaxy Ever Discovered Died Fast
RandomFactor writes:
The recently discovered galaxy XMM-2599 is three times the size of any other galaxy ever imaged. And models indicate it should have continued forming stars for well over a paltry billion years, but according to new research the supermassive galaxy only did so for about 800 Million years.
The researchers also determined that the galaxy created more than 1,000 suns' worth of stars every year during its activity peak. (For comparison, our Milky Way is currently forming just one solar mass of new stars annually.) But that peak is in the rearview mirror for XMM-2599; its star-birth engine has shut down, for reasons that remain unclear.
XMM-2599 is about 12 Billion light years from Earth, so observing the galaxy shows how it was early in the evolution of the universe, which is 13.82 Billion years old.
"Even before the universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultramassive galaxy," Benjamin Forrest, a postdoctoral researcher in the Department of Physics and Astronomy at the University of California Riverside (UCR), said in a statement.
"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," added Forrest, the lead author of a new study reporting the discovery of XMM-2599.
Such monster galaxies are predicted by theory, however star formation is not predicted to die out in this fashion.
"The predicted galaxies [...] are expected to be actively forming stars" [According to study co-author Gillian Wilson.] "What makes XMM-2599 so interesting, unusual and surprising is that it is no longer forming stars, perhaps because it stopped getting fuel or its black hole began to turn on. Our results call for changes in how models turn off star formation in early galaxies."
Journal Reference:
Ben Forrest, et al. 2020 ApJL 890 L1, An Extremely Massive Quiescent Galaxy at z = 3.493: Evidence of Insufficiently Rapid Quenching Mechanisms in Theoretical Models - IOPscience (DOI: 10.3847/2041-8213/ab5b9f)
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