What is Dark Matter and where is it found? These are two of the major
mysteries in current studies of the Universe.

Although the nature of this invisible material remains elusive, astronomers
are beginning to produce detailed maps of the Cosmos, showing its location in
relation to the ordinary matter that we can see in telescopes.

One of the world leaders in this research is Dr. Andrew Taylor (Royal
Observatory, Edinburgh), who will be presenting the most accurate image ever
obtained of the Dark Matter in a galactic supercluster at the UK National
Astronomy Meeting in Bristol on Wednesday 10 April 2002.

“Ultimately we hope that the detection of a Dark Matter particle in a
laboratory will reveal its true nature and place in physics,” said Dr.
Taylor. “But at the moment our only guide to the properties of the Dark
Matter is from Cosmology.”

The method used by Taylor, a PPARC Advanced Fellow, Dr. Meghan Gray, then a
student at the Institute of Astronomy in Cambridge, and co-workers in
Heidelberg and Imperial College London, is to take advantage of gravitational
lensing, when light from a distant galaxy is bent by the gravitational field
of matter in front of it. Such gravitational lenses provide a direct probe of
where Dark Matter is in the Universe.

Edinburgh has long been at the forefront of developing and applying methods
of using gravitational lensing to image the two-dimensional distribution of
Dark Matter and so study its properties.

In a recent study, Taylor and his colleagues have made the most detailed
analysis yet of the Dark Matter in the Abell 901/2 supercluster, one of the
largest structures in the Universe. The enormous structure, some 10 million
light years across, contains a group of galaxy clusters known as Abell 901a,
901b and Abell 902.

Their image of the Dark Matter, which covers an area of sky the size of the
full Moon, was obtained by analysing the gravitationally lensed images of
50,000 galaxies. It shows that not only do the galaxies we see lie within
larger Dark Matter clumps, but that these clumps are connected by “cosmic
filaments” – bridges of Dark Matter connecting the clusters.

The existence of these filaments has long been a prediction of the theory of
Dark Matter in the Universe, which indicated that the matter in the Universe
is distributed in an intricate network of clumps and filaments – the
so-called Cosmic Web.

More recently Taylor has developed a new method which will allow cosmologists
for the first time to make fully three-dimensional images of the Dark Matter
distribution in the Universe using gravitational lensing (Ref: Taylor, 2002,
submitted to Phys Rev Lett, astro-ph/0111605).

“Having 3-D images will allow cosmologists to put much better constraints on
the nature of Dark Matter in the Universe,” explained Taylor.

NOTE FOR EDITORS:

The existence of invisible Dark Matter has been determined from its
gravitational pull on stars and galaxies. Calculations suggest that it fills
the Universe, making up 80% of all of the matter in the Universe, and is five
times more abundant than ordinary matter. When it clumps together it seeds
the formation of galaxies. Its gravitational pull also holds together
clusters of galaxies.

Details of the supercluster research were published in the March 20th issue
of the Astrophysical Journal. (Ref: Gray & Taylor et al, 2002, ApJ, 568,
141-162, astro-ph/0111288).

The Royal Observatory, Edinburgh (ROE) comprises the UK Astronomy Technology
Centre of the Particle Physics and Astronomy Research Council (PPARC), the
Institute for Astronomy of the University of Edinburgh and the ROE Visitor
Centre.

CONTACT DETAILS:

During the National Astronomy Meeting, Dr. Taylor can be contacted via the
NAM press office (see above)

Normal contact details:

Dr. Andrew N. Taylor

Institute for Astronomy

University of Edinburgh

Royal Observatory

Blackford Hill

Edinburgh

EH9 3HJ

Tel: +44 (0)131-668-8298

Fax: +44 (0)131-668-8416

E-mail: ant@roe.ac.uk

AN IMAGE SHOWING THE DARK MATTER FILAMENTS IN SUPERCLUSTER ABELL 901/2 IS
AVAILABLE ON THE WEB AT:
http://www.roe.ac.uk/~meg/darkmatter/supercluster.html