Interactions News Wire #44-05
2 June 2005  http://www.interactions.org
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Source: PPARC
Content: Press Release
Date Issued: 2 June 2005
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Millennium Simulation - the largest ever model of the Universe

The Virgo consortium, an international group of astrophysicists from
the UK, Germany, Canada and the USA has today (June 2nd) released first
results from the largest and most realistic simulation ever of the
growth of cosmic structure and the formation of galaxies and quasars.
In a paper published in Nature, the Virgo Consortium shows how comparing
such simulated data to large observational surveys can reveal the
physical processes underlying the build-up of real galaxies and black
holes.

The "Millennium Simulation" employed more than 10 billion particles of
matter to trace the evolution of the matter distribution in a cubic
region of the Universe over 2 billion light-years on a side. It kept the
principal supercomputer at the Max Planck Society's Supercomputing
Centre in Garching, Germany occupied for more than a month. By applying
sophisticated modelling techniques to the 25 Terabytes (25 million
Megabytes) of stored output, Virgo scientists are able to recreate
evolutionary histories for the approximately 20 million galaxies which
populate this enormous volume and for the supermassive black holes
occasionally seen as quasars at their hearts.  

Telescopes sensitive to microwaves have been able to image the Universe
directly when it was only 400,000 years old. The only structure at that
time was weak ripples in an otherwise uniform sea of matter and
radiation. Gravitationally driven evolution later turned these ripples
into the enormously rich structure we see today. It is this growth which
the Millennium Simulation is designed to follow, with the twin goals of
checking that this new paradigm for cosmic evolution is indeed
consistent with what we see, and of exploring the complex physics which
gave rise to galaxies and their central black holes.

Recent advances in cosmology demonstrate that about 70 percent of our
Universe currently consists of Dark Energy, a mysterious force field
which is causing it to expand ever more rapidly. About one quarter
apparently consists of Cold Dark Matter, a new kind of elementary
particle not yet directly detected on Earth.  Only about 5 percent is
made out of the ordinary atomic matter with which we are familiar, most
of that consisting of hydrogen and helium.  All these components are
treated in the Millennium Simulation.

In their Nature article, the Virgo scientists use the Millennium
Simulation to study the early growth of black holes. The Sloan Digital
Sky Survey (SDSS) has discovered a number of very distant and very
bright quasars which appear to host black holes at least a billion times
more massive than the Sun at a time when the Universe was less than a
tenth its present age.

"Many astronomers thought this impossible to reconcile with the gradual
growth of structure predicted by the standard picture", says Volker
Springel (Max Planck Institute for Astrophysics, Garching) the leader of
the Millennium project and the first author of the article, "Yet, when
we tried out our galaxy and quasar formation modelling we found that a
few massive black holes do form early enough to account for these very
rare SDSS quasars. Their galaxy hosts first appear in the Millennium
data when the Universe is only a few hundred million years old, and by
the present day they have become the most massive galaxies at the
centres of the biggest galaxy clusters."

For Carlos Frenk (Institute for Computational Cosmology, University of
Durham) the head of Virgo in the UK, the most interesting aspect of the
preliminary results is the fact that the Millennium Simulation
demonstrates for the first time that the characteristic patterns
imprinted on the matter distribution at early epochs and visible
directly in the microwave maps, should still be present and should be
detectable in the observed distribution of galaxies. "If we can measure
the baryon wiggles sufficiently well", says Frenk, "then they will
provide us with a standard measuring rod to characterise the geometry
and expansion history of the universe and so to learn about the nature
of the Dark Energy."

"These simulations produce staggering images and represent a
significant milestone in our understanding of how the early Universe
took shape." said Professor Richard Wade, Chief Executive of the
Particle Physics and Astronomy Research Council (PPARC), the science
agency that funds UK involvement in the project. Professor Wade added
"The Millennium Simulation is a brilliant example of the interaction
between theory and experiment in astronomy as the latest observations of
astronomical objects can be used to test the predictions of theoretical
models of the Universe's history."

The most interesting and far-reaching applications of the Millennium
Simulation are still to come according to Simon White (Max Planck
Institute for Astrophysics) who heads Virgo efforts in Germany. "New
observational campaigns are providing us with information of
unprecedented precision about the properties of galaxies, black holes
and the large-scale structure of our Universe," he notes. "Our ability
to predict the consequences of our theories must reach a matching level
of precision if we are to use these surveys effectively to learn about
the origin and nature of our world. The Millennium Simulation is a
unique tool for this. Our biggest challenge now is to make its power
available to astronomers everywhere so that they can insert their own
galaxy and quasar formation modelling in order to interpret their own
observational surveys."

Notes for Editors

Virgo Consortium
The Virgo Consortium is an international grouping of scientists
carrying out supercomputer simulations of the formation of galaxies,
galaxy clusters, large-scale structure, and of the evolution of the
intergalactic medium. Although most of the members are based in Britain
and at the MPA in Germany, there are important nodes in Japan, Canada
and the United States. The primary platforms used by the consortium are
the IBM supercomputer at the Computing Centre of the Max Planck Society
in Garching and the Sun Microsystems "Cosmology Machine'' at the
Institute for Computational Cosmology of Durham University. Further
information about Virgo can be found at http://www.virgo.dur.ac.uk/

Image details
Images and animation files are available to download from
http://www.mpa-garching.mpg.de/galform/press/

Contact Details

Julia Maddock
PPARC Press Office
Tel +44 (0) 1793 442094
Email: Julia.maddock@pparc.ac.uk

Professor Carlos Frenk FRS
Institute for Computational Cosmology
Durham University
Tel: Direct line: 0191 334 3641
     Secretary:   0191 334 3635
Mobile: 07808 726080
e-mail: c.s.frenk@durham.ac.uk
Available by telephone until 27th May; thereafter by mobile or e-mail

Professor Simon White FRS
Max-Planck Institute for Astrophysics
Tel: +49 89 30000 2211
Mobile: + 49 89-170-632-9225
Email swhite@mpa-graching.mpg.de
Available by telephone until 30th May, thereafter by email or mobile
only.

Dr Volker Springel
Max-Planck Institute for Astrophysics
Tel: +49 89 30000 2238
Email vspringel@mpa-graching.mpg.de
Available by telephone until 27th May, thereafter by email only.

The Particle Physics and Astronomy Research Council (PPARC) is the
UK's strategic science investment agency. It funds research,
education and public understanding in four areas of science - particle
physics, astronomy, cosmology and space science.

PPARC is government funded and provides research grants and
studentships to scientists in British universities, gives researchers
access to world-class facilities and funds the UK membership of
international bodies such as the European Laboratory for Particle
Physics (CERN), and the European Space Agency. It also contributes money
for the UK telescopes overseas on La Palma, Hawaii, Australia and in
Chile, the UK Astronomy Technology Centre at the Royal Observatory,
Edinburgh and the MERLIN/VLBI National Facility, which includes the
Lovell Telescope at Jodrell Bank observatory.

PPARC's Public Understanding of Science and Technology Awards Scheme
funds both small local projects and national initiatives aimed at
improving public understanding of its areas of science.

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Julia Maddock
Community Press Officer

Particle Physics & Astronomy Research Council
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Tel +44 (0)1793 442094, Mobile 07901 514975
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