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News Release 24 of 67

October 27, 2011 09:00 AM (EDT)

News Release Number: STScI-2011-30

Astronomers Pin Down Galaxy Collision Rate

October 27, 2011: A new analysis of Hubble surveys, including the All-Wavelength Extended Groth Strip International Survey (AEGIS), the Cosmological Evolution Survey (COSMOS), and the Great Observatories Origins Deep Survey (GOODS), combined with simulations of galaxy interactions, reveals that the merger rate of galaxies over the last 8 billion to 9 billion years falls between previous estimates.

The galaxy merger rate is one of the fundamental measures of galaxy evolution, yielding clues to how galaxies bulked up over time through encounters with other galaxies. And yet, a huge discrepancy exists over how often galaxies coalesced in the past. Earlier measurements of galaxies in deep-field surveys made by NASA's Hubble Space Telescope generated a broad range of results: anywhere from 5 percent to 25 percent of the galaxies were merging. Results from this new study are accepted for publication in The Astrophysical Journal.

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Credit: NASA, ESA, J. Lotz (STScI), M. Davis (University of California, Berkeley), and A. Koekemoer (STScI)