Galaxy Clusters are among the largest objects in the universe. They are crucial for studying cosmology and galaxy evolution. The National Science Foundation funded South Pole Telescope, located at the Amundsen-Scott South Pole Station in Antarctica, has discovered a massive galaxy cluster around 5.7 billion light years from Earth.
The cluster, officially called SPT-CLJ2344-4243, but nicknamed the "Phoenix Cluster" because of its location in the constellation of Phoenix, is forming stars at its center at the highest rate seen anywhere in the center of a galaxy cluster and equivalent to the highest seen anywhere in the universe.
According to Michael McDonald, a Hubble Fellow at the Massachusetts Institute of Technology and the lead author of a paper on the cluster, " The mythology of the Phoenix--a bird rising from the dead--is a perfect way to describe this revived object." He added "While galaxies at the center of most clusters have been dead for billions of years, the central galaxy in this cluster seems to have come back to life."
Observations made by NASA's space-based Chandra X-ray Observatory, NSF-managed Gemini Observatory, the Blanco 4-meter and Magellan telescopes in Chile, confirm that this cluster is forming stars at the highest rate ever seen in galaxy cluster. The object is the most powerful producer of X-rays of any known cluster. The rate of hot gas cooling in the central regions of the cluster is the largest ever observed.
Scientists who were part of the SPT collaboration found the cluster using the Sunyaev-Zel'dovich (SZ) effect, by which a tiny fraction of light, that has traveled for 14 billion years across the entire observable universe to get to Earth, gets scattered to higher energies as it passes through a massive cluster.
Like other galaxy clusters, Phoenix contains an abundance of hot gas, containing more normal matter than all of the galaxies in the cluster combined. The emission from this reservoir of gas can only be detected with X-ray telescopes like NASA's Chandra X-ray Observatory.
Central galaxies in the cluster have formed very few stars over the last billions of years. Astronomers think that this is due to a super-massive black hole in the central galaxy of a cluster that pumps energy into the system, which in turn prevents the cooling of gas that could result in star formation.
With the black hole at the center of the Phoenix cluster not spewing out enough jets of energy to prevent the cooling of gases, the cluster is forming stars 20 times faster than the Perseus cluster. This pace of star birth and cooling is causing both the galaxy and the black hole to put on mass quickly- a phase which scientists say will be short-lived.
The Phoenix cluster and its central galaxy and super-massive black hole are already among the most massive known objects of their type.
The findings appeared in the online edition of the journal Nature on August 15.
by RTT Staff Writer
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