(July 9, 2015) Dark
matter may find it tougher to hide in our universe.
An international team of researchers has developed a new map
of the distribution of dark matter in the universe using data from the Dark
Energy Survey (DES).
The DES, underway at the Blanco telescope in Chile, is a
cosmological galaxy survey that will map approximately an eighth of the visible
sky. The primary aim of the DES is to better characterize dark energy – the
source of the observed accelerated expansion of the universe. But one of the ways
of doing this is through studying the distribution and evolution of another
scientific mystery: dark matter. Scientists estimate that ordinary atomic
matter makes up only one-fifth of the total mass in the universe. The remaining
mass is dark – “dark” because it does not absorb or emit light.
Scientists need a precise measurement of all the matter in
the universe and where it is located to perform cosmological experiments
accurately, said Vinu Vikraman, a postdoctoral researcher at the U.S.
Department of Energy’s Argonne National Laboratory and co-author of the study.
“We don’t know what dark matter really is or how to directly
locate it in the universe,” Vikraman said. “This map will act as a valuable
tool for cosmology to answer some of these questions, including those related
to dark energy.”
To indirectly detect dark matter, the scientists constructed
a “mass map” using weak gravitational lensing shear measurements made by the
DES. Gravitational lensing refers to the bending of light by the mass surrounding
galaxies. This bending creates a distortion, or shear, of the galaxy’s shape,
which scientists can then measure to determine the density and matter
distribution of the lens.