Astronomers unveil largest-ever map of dark matter

9 January 2012

An international team of astronomers has unveiled the latest map of the distribution of dark matter in the universe. The invisible matter has been mapped by measuring the very weak effect on the images of distant, background galaxies, being distorted as their light rays pass intervening gravitating matter on their way to our telescopes - an effect known as gravitational lensing. The results appear consistent with the current "cold dark matter" model of the universe.

The dark matter map was presented at the 219th meeting of the American Astronomical Society in Austin, Texas, together with quantitative statistical measurements of the distribution. The work was presented by principal investigators Catherine Heymans (Edinburgh University) and Ludo van Waerbeke (University of British Columbia), as part of the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Oxford astrophysicists Lance Miller and Malin Velander were responsible for parts of the delicate lensing measurement process and for modelling the distribution of dark matter around luminous galaxies.

The picture shows the four regions of the sky that were mapped at differing times of the year throughout a five-year period by the CFHT, the bright regions correspond to the regions of greatest concentration of mass, but note too the large "voids" apparently with only low density of dark matter. The Winter map corresponds to a region about a billion light years across and is approximately 9 degrees across on the sky. The inset shows the previous largest deep lensing survey with the COSMOS dataset (although larger-area, shallower surveys also exist), also the size of the full moon to scale.