Astronomers reach new frontiers of dark matter

The University of British Columbia
The University of Edinburgh
Canada-France-Hawaii Telescope

News Release

Issued: Monday 9 January 2012

FOR RELEASE: 09:30 a.m. EDT, January 9, 2012

For the first time, astronomers have mapped dark matter on the largest scale ever observed. The results, presented by Dr Catherine Heymans of the University of Edinburgh, Scotland, and Associate Professor Ludovic Van Waerbeke of the University of British Columbia, Vancouver, Canada, are being presented today to the American Astronomical Society meeting in Austin, Texas. Their findings reveal a Universe comprised of an intricate cosmic web of dark matter and galaxies spanning more than one billion light years.

An international team of researchers lead by Van Waerbeke and Heymans achieved their results by analysing images of about 10 million galaxies in four different regions of the sky. They studied the distortion of the light emitted from these galaxies, which is bent as it passes massive clumps of dark matter during its journey to Earth.

Their project, known as the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), uses data from the Canada-France-Hawaii Telescope Legacy Survey. This accumulated images over five years using the wide field imaging camera MegaCam, a 1 degree by 1 degree field-of-view, 340 Megapixel camera on the CFHT in Hawaii.

Galaxies included in the survey are typically six billion light years away. The light captured by the images used in the study was emitted when the Universe was six billion years old – roughly half the age it is today.

The team’s result has been suspected for a long time from studies based on computer simulations, but was difficult to verify owing to the invisible nature of dark matter. This is the first direct glimpse at dark matter on large scales showing the cosmic web in all directions.

Professor Ludovic Van Waerbeke, from the University of British Columbia, said: “It is fascinating to be able to ‘see’ the dark matter using space-time distortion. It gives us privileged access to this mysterious mass in the Universe which cannot be observed otherwise. Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics.”

Dr Catherine Heymans, a Lecturer in the University of Edinburgh’s School of Physics and Astronomy, said: “By analysing light from the distant Universe, we can learn about what it has travelled through on its journey to reach us. We hope that by mapping more dark matter than has been studied before, we are a step closer to understanding this material and its relationship with the galaxies in our Universe.”

Dr Christian Veillet, CFHT Executive Director, said “This dark matter study illustrates the strong legacy value of the CFHT Legacy Survey which is now enabling exciting results obtained by teams from many nations which use the images retrieved from the Canadian Astronomy Data Centre where they are archived and publicly available”.

Dr Thomas Kitching, the Cosmology Working Group coordinator, based in the School's Institute for Astronomy at the University of Edinburgh said "The dark matter map we have produced looks back over 75% of the age of the Universe, to a time when it was very different to today. By tracking the evolution of the Universe over cosmic time, the team at Edinburgh will investigate how dark energy has come to dominate the present day Universe."

"Over the next few months we will be using this data to map the evolution of the expansion of the Universe and learn about dark energy, which is causing the expansion of the Universe to accelerate. We will test theories of gravity itself to determine if Einstein's general relativity is correct or not. We will also use it to determine the properties of neutrinos, ghostly particles that interact with normal matter only very weakly."

Professor Lance Miller, from Oxford University said: “This result has been achieved through advances in our analysis techniques which we are now applying to data from the Very Large Telescope’s (VLT) Survey Telescope in Chile.”

Emma Grocutt a PhD student at the University of Edinburgh's Institute for Astronomy said "Gravitational lensing is a unique tool for probing the mysteries of the cosmos. It is directly sensitive to the position and amount of dark matter in the Universe , a fact the CFHTLenS team have exploited to map its structure.The CFHT Lensing Survey is the largest of its kind ever conducted, and an unprecedented amount of data will enable us to learn more about dark matter and dark energy than ever before. Such a large data set always comes with its own set of unforeseen problems, however, and the team has worked extremely hard to make sure we understand the data thoroughly so we can be sure our results are as accurate as possible."

Professor Koen Kuijken, from Leiden University, said: “Over the next three years we will image more than 10 times the area mapped by CFHTLenS, bringing us ever closer to our goal of understanding the mysterious dark side of the Universe.”

Notes to editors

Images

Dark Matter Distribution

Image Caption: The observations show that dark matter in the Universe is distributed as a network of gigantic dense (white) and empty (dark) regions, where the largest white regions are about the size of an Earth moon on the sky. Credit: Van Waerbeke, Heymans and the CFHTLenS Collaboration

 

More images are available at: CFHT

Media Contacts

Catriona Kelly
University of Edinburgh
Tel: +44 131 651 4401
Email: Catriona.Kelly@ed.ac.uk

Brian Lin
University of British Columbia
Tel: 001 604 822 2234
Email: Brian.Lin@ubc.ca

Jean-Charles Cuillandre
CFHT
Tel: 001808 885 7944
Email: cuillandre@cfht.hawaii.edu

Links

CFHTLenS website

This research was supported by the European Research Council, Natural Sciences and Engineering Research Council of Canada, the Canadian Institute for Advanced Research and the Canadian Astronomy Data Centre.