This galaxy cluster should be much cooler than it actually is.
Lingxiao Yuan
A young cluster of galaxies in the early Universe is challenging our understanding of how these enormous structures formed and evolved. The gas that fills this clump, called SPT2349-56, is much hotter and more widespread than it should be, and researchers don't understand why.
Dazhi Zhou from the University of British Columbia in Canada and his colleagues observed the cluster with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and found that towards its center intracluster gas has a temperature of at least several tens of millions of degrees.
“The surface temperature of the sun is several thousand degrees Celsius, so this entire region is hotter than the sun,” says Zhou. “We conservatively estimate that it is 5 to 10 times hotter than expected from modeling – this is very surprising since this type of hot gas was not expected to appear until billions of years later.”
SPT2349-56 is located in the early Universe, approximately 1.4 billion years after the Big Bang. “This type of gas should still be cool and less abundant because these young clusters are still accumulating and warming up their gas,” Zhou says. This cluster, the only one of its kind seen so far, looks much more mature than it should.
Its strange heat may have been due to the presence of several especially active galaxies its members include at least three who emit enormous jets of energy. These jets and frequent bursts of star formation may be heating the gas much faster than we previously thought.
“This actually opens a new window showing a phase of cluster evolution that we have never seen before,” says Zhou. He and his team are planning follow-up observations to find more hot young clusters like this one, in hopes of finding out just how unusual it really is.
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