Researchers led by scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have released a major catalog of galaxy clusters, giving scientists a powerful new tool for studying how the universe grew and changed over billions of years.
Using exceptionally sensitive measurements of the cosmic microwave background (CMB) — the faint afterglow of the Big Bang — the multi-institutional team confirmed 7,190 of 8,892 candidate galaxy clusters. The catalog is based on five years of observations from the SPT-3G experiment at the U.S. National Science Foundation (NSF) Amundsen Scott South Pole Station in Antarctica.
Of those confirmed clusters, roughly 20% do not appear in any previous catalog, but the findings go even further: For 67% of the sample — some 4,824 systems — this marks the first time the hot gas within these clusters has ever been detected, making the majority of the catalog a genuinely new window into the large-scale structure of the universe.
“Our analysis draws on the SPT-3G’s phenomenally deep CMB data to open a new window onto the ancient universe,” said Lindsey Bleem, a physicist at Argonne and lead author of the study. “It’s a new milestone for cluster cosmology to have this catalog as a resource. It will be the core of many, many studies over the years to come.”
The SPT-3G camera, mounted on the South Pole Telescope, was upgraded in 2017 with 16,000 detectors built at Argonne. The catalog spans about 4% of the sky and includes roughly 1,800 clusters that date back more than 7.8 billion years.
The team found the clusters by looking for distortions they cause in the CMB known as the Sunyaev-Zeldovich effect, which allows researchers to image clusters as shadows on the backdrop of the CMB.
Galaxy clusters — enormous collections of hundreds to thousands of galaxies bound by gravity — are among scientists’ most powerful tools for probing dark matter, dark energy and cosmic structure.
Future work will focus on refining cluster mass measurements and using the catalog to test models of the universe. Upcoming surveys, including the Legacy Survey of Space and Time at the Vera C. Rubin Observatory and the European Space Agency’s Euclid mission, are expected to provide optical confirmation of even more distant clusters in the SPT-3G data.
The South Pole Telescope is funded primarily by the NSF and the DOE Office of Science, Office of High Energy Physics, and is operated by a collaboration led by the University of Chicago. Optical data used to confirm the clusters came from the DOE/NSF-supported Dark Energy Survey.
The Dark Energy Survey is jointly supported by the DOE Office of Science and the NSF. Learn more about the collaboration and the funding for this project.
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