Community Research and Development Information Service - CORDIS

Final Activity Report Summary - DUEL (The Dark Universe with Extragalactic Lensing)

Cosmic Shear with DUEL Cosmic Shear is a weak gravitational lensing effect which distorts the images of distant galaxies due to the deflection of light by the gravitational pull of intervening matter. These distortions alter the shape of galaxy images by only a few per cent. With high-accuracy imaging and advanced image analysis methods these distortions can be detected and used to map the pattern and growth of Dark Matter clustering. Dark Matter contributes 20% to the energy-density of the Universe and drives the formation of galaxies, but we don't yet know what it is. Cosmic Shear also depends on the history of the expansion of the Universe and so is a probe of the nature of the mysterious Dark Energy which contributes 70% of the energy budget of the Universe and is causing the expansion to accelerate.

The DUEL Network was set up in 2007 to provide the European Cosmological community with the expertise and methods to carry out Cosmic Shear Surveys on three of the largest ground-based imaging and multi-wavelength galaxy surveys: the Canada-France-Hawaii Telescope (CFHT) Survey; the European VLT Survey Telescope Kilo-Degree Survey (VST-KIDS) and the US-European Panoramic Survey and Rapid Response System (Pan-STARSS-1; PS1) Survey. When complete these will have imaged 170, 1500, and 20,000 square degrees of the sky. DUEL Nodes were established at Edinburgh, Paris, Leiden, Bonn, Munich, Heidelberg, Naples and Vancouver and 7 Early Stage Researchers and 7 Experience Researchers appointed. Over the last four year, the DUEL Network has established a Cosmic Shear community and DUEL Fellows have helped make the measurement of the shear effect from the small distortions in galaxy images reliable. They have developed new data analysis methods which have been applied to the CFHT and PS1 Surveys, and shown that the massive data-sets from these surveys can be dealt with. The analysis of the CFHT Survey has shown that Cosmic Shear data can be understood to a very high degree and its systematics controlled.

In doing so we have developed a much better understanding of astronomical measurements and turned telescopes into high-precision instruments. In addition, DUEL has made non-cosmology systematic testing and blind analysis the standard for Cosmic Shear analysis, and developed Cosmic Shear simulations to test new methods and understand the statistical significance of Cosmic Shear results. The CFHT Survey is now under control of its systematics and we are finalizing Dark Matter maps, and cosmological parameter estimation.

A series of 20 papers will appear later this year will all results in. The PS1 Survey is in progress and much of what DUEL has learnt is being applied. VST-KIDS is about to start its survey, and again the wealth of knowledge from CFHT and PS1 will be used to carry out its analysis.

Finally, as well as carrying out the analysis of current survey, DUEL has supported the development of the Euclid Satellite Mission proposal to the European Space Agency. If selected in September 2011 this will launch in 2018 and carry out a five-year mission to image the whole sky for Cosmic Shear. DUEL has been key to building the science case for measuring Dark Matter, Dark Energy and testing Einstein's Theory of Gravity. This will be DUEL's final legacy.

Reported by

University of Edinburgh
Old College South Bridge
EH1 1HN Edinburgh
United Kingdom
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