Astronomers discover once-productive galaxy that fizzled out in early universe

An international team of astronomers, including a researcher from UCI’s Department of Physics & Astronomy, has found an ultramassive galaxy as it existed more than 12 billion years ago. Galaxy XMM-2599 was extremely productive early on – hatching more than 300 billion suns by the time the universe had its 1 billionth birthday (it’s now about 13.7 billion years old) – but the astronomers observed that it suddenly stopped forming stars before the universe was 2 billion years old. The group made its discovery using observations from the W.M. Keck Observatory’s multi-object spectrometer for infrared exploration, known as MOSFIRE; the study was published today in The Astrophysical Journal. The researchers suggest that they may have caught the galaxy in an inactive phase and are pondering what its evolution may hold. Co-author Michael Cooper, UCI professor of physics & astronomy, said: “Perhaps during the following 11.7 billion years of cosmic history, XMM-2599 will become the central member of one of the brightest and most massive clusters of galaxies in the local universe. Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these two outcomes.” The team has been awarded more time at the W.M. Keck Observatory, in Hawaii, to follow up on questions prompted by XMM-2599.