Searching For Dark Matter Using Gravitational Lensing

A MATTER OF DARK UNDERSTANING - Part One

Numerical simulation showing the distribution of dark matter in a large volume of the universe. The box shown spans a distance of about 1 billion light-years. The structures are displayed so that the brighter regions have a higher density (that is, more dark matter) than the darker regions.

The dark matter is concentrated into a web-like distribution of filaments that intersect at dense nodes where great clusters of galaxies are expected to form and become visible. At the rear of the cube (to the left), three blue disks represent three distant galaxies.

The yellow lines that cross the box represent light rays from those galaxies propagating through the universe. In the absence of intervening matter, the light would travel on straight lines but in the presence of matter, the paths of the rays are evidently deflected by the gravitational effects of the clumpy matter (the breaks in the yellow lines illustrate the light passing behind a clump of dark matter).

The light from a distant galaxy rarely encounters a clump of mass to strongly bend the light and cause an easily seen distortion. Instead the individual light rays suffer a series of small deflections such that an observer located at the front of the box (to the right), sees that the images of all the galaxies in some small patch of the sky, near to one of our test galaxies say, are all very slightly elongated in a common direction determined by the distribution of dark matter along that particular line of sight. This gravitational distortion is expected to be very small and requires a careful statistical treatment on many patches over the sky but has now been measured by the French team. Numerical simulation by S. Colombi IAP

Searching For Dark Matter Using Gravitational Lensing
Kamuela - March 7, 2000 - Using state-of-the-art image analysis software, largely developed at the TERAPIX data analysis and processing center in Paris, the team was able to analyze the light from 200,000 very distant and faint galaxies, looking for the minute distortions that, in theory, should occur as the light passes through the gravitational fields of intervening dark matter.

Using this information the team has developed the first "map" of dark matter in that area of sky, allowing researchers to visualize how it condensed out of the early universe and distributed itself over the course of time.

The analysis has revealed the presence of a vast matrix of interconnected dark matter. The result is not only a significant technological feat, but also a major advance in astronomy and cosmology.

According to Dr. Greg Fahlman, Director of the Canada-France-Hawaii Telescope, the results are but a preliminary view of what the future is promising.

"By 2002 we will have a new wide-field imaging camera on the telescope that will cover, with improved sensitivity, an area of sky 3 times greater than the current camera. This new instrument will greatly enhance our ability to map the cosmic distribution of dark matter," said Fahlman.

MegaCam, as this new camera is called, will provide astronomers with the data they need to develop significantly more accurate models of the universe.

"Our goal," Fahlman adds, "is to help create the first distribution maps of dark matter across the sky, similar to the distribution maps you currently see for galaxies."

Click For Part One Of This Report

The Canada-France-Hawaii Telescope is funded through the National Research Council of Canada (NRC), the Centre National de la Reserche Scientifique (CNRS) in France, and the University of Hawaii.

More images and information on this research

Intitut d'Astrophysique de Paris

Canada-France-Hawaii Telescope Telephone

SPACE SCIENCE
illustration only Scientists Claim To Have Detected Dark Matter
Stanford - February 28, 2000 - A group of researchers claim to have achieved the world's best discrimination in the search for dark matter, which some scientists think makes up more than 90 percent of the mass of the universe.

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