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Computing the X-Ray Universe: Overview

Incorporating both gas dynamics and mixed dark matter, a KRONOS code was run on NCSA's 512-node Connection Machine. Each of the 512 volumes of the simulation was assigned to a single processor node on the CM-5. The simulation, which predicts the patterns of X-rays emitted from hot clusters of primordial cosmic gas, the precursors of giant clusters of galaxies, was "the first [of its kind] to be sufficiently comprehensive to make predictions that can be compared with observations." (Mike Norman, NCSA/University of Illinois at Urbana-Champaign).

The first five movies introduce X-ray clusters and their significance to cosmology and present the methodology underlying the simulation. A 2-dimensional simulation is portrayed to illustrate the basic mechanism of structure formation by gravity and to introduce the notion of co-moving coordinates in an expanding universe.

Next presented are three movies (6a, 6b, 7) depicting volumetric renderings of the simulation volume as it is evolved forward in time by the computer, from shortly after the Big Bang to the present. Both gas density and temperature are shown as a function of time.

Then, the predicted evolution of X-ray luminosity associated with formation of hot dense gas clusters is shown (8).

Finally, you can "fly-through" the computing box to see close-ups of clusters and get a better view of their three-dimensional structure. Gas density (and temperature evolution) are/is presented followed by the predicted pattern of X-ray luminosity (9, 10, 11).

Owing to the limitations of bandwidth, we are limited to offering the movies only as "micons" and at rather low resolution. The still image shows the predicted X ray luminosity patterns more clearly than the movies.

The Simulation "Recipe"

In addition to the gas, 50 million dark matter particles were evolved which cluster in very much the same way as the gas. One-third of the dark matter particles were "cold" and the remaining two-thirds were massive neutrinos with an assumed mass of 7 electron volts. Further details, including the calculation parameters of the simulation, can be obtained from the abstract and a full technical paper (postscript file) reporting this research.


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NCSA. Last modified, 10/18/95