A ‘finger’ of the Universe’s dark-matter skeleton, which ultimately dictates where galaxies form, has been observed for the first time bridging the galaxy clusters Abell 222 and Abell 223 2.7 billion light-years away by an international team of astrophysicists using a technique that could eventually help astrophysicists to understand the structure of the Universe and identify what makes up the mysterious invisible substance known as dark matter.
"Dark matter really governs structure formation," said study leader Joerg Dietrich, an astrophysicist at the University Observatory Munich in Germany. "The galaxy clusters and the filaments are mostly made up of dark matter. The normal matter just follows the distribution of dark matter."
The discovery of these dark-matter filaments, about 58 million light-years from end to end, are predicted to contain more than half of all matter in the Universe, was published online Wednesday by the journal Nature.
According to the standard model of cosmology, visible stars and galaxies trace a pattern across the sky known as the cosmic web, which was originally created by dark matter. These long strands of dark matter bridge clusters of galaxies formed at the nodes of the cosmic web, where these filaments intersected.
By examining X-rays from plasma in the filament, observed by the XMM-Newton spacecraft2, the team calculated that no more than 9% of the filament's mass could be made up of hot gas. The team's computer simulations suggest that roughly another 10% of the mass could be due to visible stars and galaxies, the balance dark matter, said Dietrich.
“What’s exciting is that in this unusual system we can map both dark matter and visible matter together and try to figure out how they connect and evolve along the filament,” says Mark Bautz, an astrophysicist at the Massachusetts Institute of Technology .
“This will complement direct dark-matter searches, for example at the Large Hadron Collider,” says Alexandre Refregier, a cosmologist at ETH Zurich, the Swiss Federal Institute of Technology in Zurich.
The Daily Galaxy via Nature doi:10.1038/nature.2012.10951
Image credit: Joerg Dietrich, University of Michigan/University