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Hot Gas and Dark Matter in Clusters of Galaxies

Clusters of galaxies are some of the largest structures in the universe. Studying them provides important clues as to the make-up of the universe, with regard to both how structures form and the chemical composition of the universe.

The mass within a cluster is divided up between the stars (about 10% of the cluster mass), a hot X-ray emitting gas (20% of the cluster), and dark matter (the remaining 70%). Scientists now know that the gravitational effect of the dark matter is responsible for holding the cluster together. But the nature and detailed distribution of the dark matter is still a mystery.

optical image of galaxy cluster
Optical image of the Centaurus cluster of galaxies.
x-ray image of galaxy cluster
Corresponding X-ray image of the Centaurus cluster of galaxies.

The X-ray emitting gas permeates the cluster, and provides clues about the dark matter in the cluster. Suzaku's ability to determine the energy of X-rays to high precision will aid in the study of the X-ray gas. Suzaku will be able to measure the motion of the this gas. We know that, overall, it is falling into the center of the cluster. As it falls in, it should cool, and the atoms in the gas should radiate with their characteristic energies. However, observations previous to Suzaku do not show all the emission lines that are expected. Suzaku has the sensitivity to determine if these lines are really there.

In addition, Suzaku's observations will be able to help scientists decide which models best describe the data: those that show the gas is turbulent or those that show the gas temperature distribution is smooth.

Publication Date: June 2005

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