New details on the galaxy cluster SPT2349-56, observed just 1.4 billion years after the Big Bang, reveal three supermassive black holes likely responsible for heating its gas to five times hotter than models predict—building on initial ALMA observations reported earlier this week.
As detailed in the initial discovery (reported January 5), astronomers led by Dazhi Zhou of the University of British Columbia have confirmed that SPT2349-56 contains intracluster gas at temperatures of several tens of millions of degrees—hotter than the Sun's surface and far exceeding expectations for such an early, compact structure spanning about 500,000 light-years in its core, comparable to the Milky Way's halo.
The cluster hosts over 30 tightly packed active galaxies producing stars at a rate more than 5,000 times that of the Milky Way. Using the Atacama Large Millimeter/submillimeter Array (ALMA), including Canadian contributions, the team measured the gas temperature via the Sunyaev-Zeldovich effect, verifying the extreme heat after months of analysis.
"We didn't expect such a hot cluster atmosphere so early," Zhou said. Co-author Scott Chapman of Dalhousie University and UBC added, "Three recently discovered supermassive black holes were already pumping huge amounts of energy into the surroundings, shaping the young cluster more violently than theorized."
This challenges gradual heating models, suggesting rapid feedback from black holes and star formation. The cluster's maturity implies a new phase in early cluster evolution. Future studies will explore these dynamics, with further ALMA observations planned. The results appear in Nature (January 5).