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Press Release 05-207
Galaxy Collisions Dominate the Universe
Massive galaxies form by mergers
December 7, 2005
A study using hundreds of images from two of the deepest sky surveys ever conducted has confirmed what astronomers have long suspected: no galaxy is an island.
Quite the opposite, says Yale astronomer Pieter van Dokkum, lead author of the survey team's report in the Dec. 2005 issue of the Astronomical Journal. Galaxies are in constant interaction with one another. Indeed, that's how theorists believe most galaxies formed in the first place, with the big ones getting bigger through the collision and merger of smaller ones.
For a long time, van Dokkum adds, the only exceptions seemed to be the giant elliptical galaxies. These immense, featureless blobs not only contain some of the oldest stars in the universe, but look as if nothing had disturbed them for many billions of years, since shortly after the big bang.
Now, closer examination tells a different story. Using data from two recent deep surveys done with the National Science Foundation's 4-meter telescopes at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, known as the NOAO Deep Wide-Field Survey and the Multiwavelength Survey by Yale/Chile, van Dokkum an his colleagues find that 53 percent of the elliptical galaxies in their sample show complex tails and streamers of stars--the classic signs of galaxies in collision.
"Our study found these common massive galaxies do form by mergers," says van Dokkum. "It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect."
For more information, see the news release from the National Optical Astronomy Observatory.
-NSF-
Media Contacts
Douglas Isbell, NOAO (520) 318-8214 disbell@noao.edu
M. Mitchell Waldrop, NSF (703) 292-7752 mwaldrop@nsf.gov
Janet Rettig Emanuel, Yale University 203) 432-2157 janet.emanuel@yale.edu
Principal Investigators
Pieter van Dokkum, Yale University (203) 432-3019 dokkum@astro.yale.edu
Related Websites
Yale news release: http://www.yale.edu/opa/newsr/05-12-06-01.all.html
Images, animation of galaxy growth, and published paper: http://www.astro.yale.edu/dokkum/mergers/
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