Probing dark energySPT teams uses new method to discover faraway galaxy clustersPosted October 17, 2008
Scientists have studied the night sky for thousands of years searching for clues to help them understand the universe. The South Pole Telescope (SPT) More Information
Staniszewski is the lead author on the multi-institution collaboration's paper, “Galaxy clusters discovered with a Sunyaev-Zel'dovich effect survey The technique relies on an effect that galaxy clusters have on the Cosmic Microwave Background (CMB) The 10-meter South Pole Telescope’s millimeter-wave camera captures images of the CMB, radiation left over from 270,000 years after the Big Bang ![]() Photo Credit: Keith Vanderlinde/Antarctic Photo Library
The SPT and Dark Sector Lab during the South Pole winter in 2008.
These galaxies, Staniszewski says, are likely billions of light years away and about seven billion years old. Part of the data set was taken by Staniszewski during his winter stay at the South Pole “The theory of how galaxy clusters imprint a signal on the CMB has been around for nearly 40 years, when two Russian physicists first proposed it in 1969,” Staniszewski said. “The SZ effect has been seen in clusters that were already identified by optical and x-ray observations, but no one had yet used it to discover a brand new galaxy cluster. These are the first galaxy clusters discovered using this method.” The SPT will produce a larger catalog of new clusters with more data and analysis. “These three new clusters are just the tip of the iceberg," Ruhl said. “The full survey is what will help us achieve our ultimate goal, which is to understand dark energy.” “The expansion of the universe is accelerating, and because of that we believe that dark energy dominates the energy density of the universe. Dark energy provides a negative pressure, or repulsive force, that accelerates the expansion, rather than slowing it down like the attractive force of gravity does,” Staniszewski said. “We're trying to figure out what dark energy actually is, and it turns out that a survey of galaxy clusters can be used to trace the expansion history of the universe, which can tell you about the dark energy." Gravity works to pull pockets of galaxies together, into clusters, a process that is more effective at early times when matter is dense. Dark energy speeds up the expansion of the universe and spreads out the matter, which slows down clustering. Counting the number of galaxy clusters as a function of time throughout the history of the universe can therefore be used to understand dark energy. The SPT science team, led by principal investigator John Carlstrom at the University of Chicago NSF-funded research in this story: John Carlstrom, University of Chicago; John Ruhl, Case Western Reserve University; Award No. 0638937 |