Astronomers Find Burned Out Galaxies in Ancient Universe – Tufts Now

A team of astronomy researchers has discovered a surprising fact from the first couple of billion years of the universe: there were at least some large groups of galaxies that were already burning out at the time, contrary to the general pattern of galaxies having vigorous star formation then.

The massive grouping of at least 38 young galaxies that was discovered, called protocluster MAGAZ3NE J0959, is about 11.8 billion light-years away from Earth, and was found using the W. M. Keck Observatory in Hawaii. At the center of MAGAZ3NE J0959 is an ultra-massive galaxy with more than 200 billion suns.

The discovery of this protocluster with a population dominated by ultra-massive galaxies with halted star-formation activity was surprising, said Danilo Marchesini, a Tufts professor of astronomy who was part of the research team. It shows that even in the early universe there was already a great range of diversity in terms of the properties of galaxies.

We were not expecting this, and this finding raises new exciting questions, said Marchesini, who was joined on the project by Tufts postdoctoral researcher Marianna Annunziatella.

One issue is if the censuses of distant protoclusters are biased or incomplete, he said. The fact that previously reported protoclusters at this epoch were found to contain mostly star-forming galaxies may be evidence that our view of dense environments in the early universe is at least incomplete, or most likely biased, as finding distant quiescent galaxies is much harder than finding actively star-forming galaxies.

The research team, led by University of California at Riverside astronomers Ian McConachie and Gillian Wilson, reported their findings in the Astrophysical Journal. In marked contrast to protoclusters previously reported at this epoch which have been found to predominantly contain star-forming members, MAGAZ3NE J0959 was found to have an elevated fraction of quiescent galaxies, the research team wrote. This suggests that protoclusters exist in a diversity of evolutionary states in the early Universe.

Looking ahead, the researchers note in the paper that future ground and space telescopes with the capability to survey significantly wider areas, such as the James Webb Space Telescope . . . will undoubtedly facilitate the discovery of larger samples, allowing better insight into the uniqueness of MAGAZ3NE J0959, and helping to propel our understanding of the formation of UMGs [ultra-massive galaxies] and protoclusters into the even earlier Universe.

Taylor McNeil can be reached at taylor.mcneil@tufts.edu.

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Astronomers Find Burned Out Galaxies in Ancient Universe - Tufts Now