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NAS FEATURED NEWS
Columbia Used to Generate Massive Simulation of Dark Matter Halo Surrounding Milky Way
A recent simulation showing unprecedented detail of the dark matter halo surrounding the Milky Way will aid us in understanding the evolutionary history of our galaxy.
12.14.06
Researchers from the University of California, Santa Cruz (UCSC) recently employed the Columbia supercomputer to run the largest simulation (to date) of the formation and evolution of the dark matter halo that envelopes the Milky Way galaxy. These results, using 300-400 of Columbia's processors per run for a total 320,000 processor-hours, show substructures within the halo in detail that has never before been captured.
"We [have found] almost 10,000 subhalos, about one order of magnitude more than in any past simulations, and some of our subhalos exhibit 'subsubstructure.' This was expected theoretically, but we have shown it for the first time in a numerical simulation," explained Piero Madau, professor of astronomy and astrophysics at UCSC.
Caption: (Above right) Projected dark matter density-square maps of the simulated Milky Way-size halo at 13.3 billion years ago, 460 million years after the Big Bang.
(Click on image to enlarge)
This simulation starts at about 50 million years after the alleged Big Bang and calculates the interactions of 234 million particles of dark matter over 13.7 billion years of cosmological time to produce a halo on the same scale as the Milky Way's. The simulation is a valuable tool for understanding the evolutionary history of our galaxy. It is also useful for observational astronomers studying the oldest stars in our galaxy, providing a link between current observations and earlier phases of galaxy formation.
"The first small galaxies formed very early, about 500 million years after the Big Bang, and there are still today stars in our galaxy that formed at this early time, like a fossil record of early star formation," explained Juerg Diemand, a Hubble postdoctoral fellow at UCSC. "Our simulation can provide the context for where those old stars came from, and how they ended up in dwarf galaxies and in certain orbits in the stellar halo today."
Although the nature of dark matter remains a mystery, it appears to account for about 82 percent of the matter in the universe. As a result, the evolution of structure in the universe has been driven by the gravitational interactions of dark matter. Initially, gravity acted on slight density fluctuations present shortly after the Big Bang to pull together the first clumps of dark matter. These grew into larger and larger clumps through the hierarchical merging of smaller "originators" -- the very process the UCSC researchers simulated on Columbia.
+ View animation (MPG-11MB - no audio)
For more information on the Milky Way Galaxy simulation, contact:
Juerg Diemand,
diemand@ucolick.org
For information about NASA and agency programs on the Web, visit
http://www.nasa.gov/home/
- Holly A. Amundson
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