An international team of astronomers led by scientists at the University of California, Riverside, has found an unusual monster galaxy that existed about 12 billion years ago, when the universe was only 1.8 billion years old. Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.
The research team used spectroscopic observations from the W. M. Keck Observatory’s powerful Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance.
“In this epoch, very few galaxies have stopped forming stars, and none are as massive as XMM-2599,” said Gillian Wilson, a professor of physics and astronomy at UCR in whose lab Forrest works. “The mere existence of ultramassive galaxies like XMM-2599 proves quite a challenge to numerical models. Even though such massive galaxies are incredibly rare at this epoch, the models do predict them. The predicted galaxies, however, are expected to be actively forming stars. 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.”
The team found XMM-2599 formed more than 1,000 solar masses a year in stars at its peak of activity — an extremely high rate of star formation. In contrast, the Milky Way forms about one new star a year.
Source: University of California – Riverside. “Astronomers discover unusual monster galaxy in the very early universe.” ScienceDaily. ScienceDaily, 5 February 2020. <http://www.sciencedaily.com/releases/2020/02/200205110541.htm>.