Yesterday, we reported that an international team of astronomers Using W. M. Keck Observatory on Maunakea in Hawaii, led by scientists at the University of California, Riverside, found an strange monster galaxy that existed about 12 billion years ago, when the universe was only 1.8 billion years old, or 13 percent of its current age of 13.8 billion years. The team found that the galaxy, dubbed formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.
“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,” said Benjamin Forrest, a postdoctoral researcher in the UC Riverside Department of Physics and Astronomy and the study’s lead author. “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 used spectroscopic observations from Keck Observatory’s powerful Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), to make detailed measurements of XMM-2599 and precisely quantify its distance. The image above set shows the possible evolution of XMM-2599, from a massive, dusty, star-forming galaxy (left), to an inactive red galaxy (center), and then perhaps turning into a bright cluster galaxy (right). ( NRAO/AUI/NSF, B. SAXTON; NASA/ESA/R. FOLEY; NASA/ESA/STSCI, M. POSTMAN/CLASH)
“It’s exciting to see one of our most in-demand instruments successfully characterize such a rare, ancient galaxy with a short life span,” said co-author Percy Gomez, an astronomer at Keck Observatory. “It took many hours-long observations, some as much as nine hours each, to determine XMM-2599’s distance and mass. It’s fulfilling to be a part of a team that continues pushing Keck and MOSFIRE to probe deeper into the mysteries about the origins of massive galaxies and protoclusters.”
The research 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.
“XMM-2599 may be a descendant of a population of highly star-forming dusty galaxies in the very early universe that new infrared telescopes have recently discovered,” said Danilo Marchesini, an associate professor of astronomy at Tufts University and a co-author on the study.
The evolutionary pathway of XMM-2599 is unclear, but 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,” he said. “Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these two outcomes.”
The Daily Galaxy, Max Goldberg, via Keck Observatory