12 January 2005 (Not for
distribution until 0400 AEDT 12 January 2005, 1700 GMT on January 11th)
Galaxy patterns reveal missing
link to Big Bang
Australian astronomers from the Anglo-Australian Observatory, The
National University, CSIRO and the University of New South Wales,
with their UK colleagues, today announced that they have found the
link' that directly relates modern galaxies like our own Milky Way to
Hot Big Bang that created our Universe 14 thousand million years ago.
This is the result of a 10-year effort to map the 3D distribution in
of 220,000 galaxies using the 3.9-m Anglo-Australian Telescope (AAT) in
South Wales - a project called the 2-degree Field Galaxy Redshift Survey
This survey was almost ten times larger than any previous such study.
It measured in detail patterns in the distribution of galaxies, on
from 100 million to 1 billion light-years.
Subtle features in these patterns were set by physical processes that
operated when the Universe was very young, and reveal the 'missing link'
between present-day galaxies and the Big Bang.
"This is an enormously important finding," said Dr Matthew Colless,
of the Anglo-Australian Observatory and Australian leader of the 2dFGRS
team. "Although there have been hints before of these features, this is
first high-confidence detection. We've confirmed that gravity was the
driving force that created today's galaxies."
"The same features tell us the mass density of the Universe - the
mass for a given volume of space - with an uncertainty of less than
"This survey, coupled with a few other lines of enquiry, has given us
extremely good measurements of two major constituents of the Universe -
dark matter and dark energy," said 2dFGRS team member Dr Warrick Couch
the University of New South Wales.
Measuring the galaxies' s distances and modelling their distribution in
space had taken "more than a decade of work" by a team of over 30
said Dr Bruce Peterson of the ANU's Research School of Astronomy and
Astrophysics, the 2dFGRS team member who constructed the database for
Independent corroboration of the 2dFGRS result was also announced today
the US-led Sloan Digital Sky Survey (SDSS), at the winter meeting of the
American Astronomical Society in San Diego. The SDSS team used a sample
46,000 highly luminous red galaxies and a different method of analysis
the 2dFGRS team's. "Happily, the two groups' conclusions are
said 2dFGRS team member Dr Joss Hawthorn of the Anglo-Australian
The robotic 2dF instrument, which made the survey possible, was
built by the Anglo-Australian Observatory. It measures the 'redshifts'
galaxies - a change in the light they emit that varies with distance,
which can be used as a measure of distance. "The 2dF instrument is the
world's most efficient machine for measuring redshifts," said 2dFGRS
member Dr Russell Cannon, a former director of the Anglo-Australian
Observatory during whose term the 2dFGRS had been initiated.
Theorists in the 1960s suggested that the primordial seeds of galaxies
should be seen as 'ripples' - a pattern of hotter and cooler spots - in
cosmic microwave background (CMB). This CMB is heat radiation left over
the Big Bang. We see the CMB as it was when the Universe was only about
350,000 years old.
The ripples in the CMB were first seen in 1992 by NASA's COBE
until now, no-one had been able to definitely show how they were
to galaxy formation.
Astronomers use a statistic called the 'power spectrum' to
describe the pattern of spots in the CMB. A plot of the power spectrum
peaks and troughs in it, and describes how the spots are clustered on
different scales. The 2dFGRS team has produced the same kind of power
spectrum for the galaxies that it mapped out.
"Features in the 2dFGRS power spectrum match up with features in the
spectrum of the CMB," said 2dFGRS team member Dr Simon Driver of the
Research School of Astronomy and Astrophysics. "This leaves no doubt
we've finally identified the origin of galaxies."
Weighing the Universe
The same features in the power spectrum have allowed the 2dFGRS team to
'weigh' the Universe with unprecedented accuracy.
These features - called the 'baryon wiggles' - contains information
the contents of the Universe; in particular about the amount of ordinary
matter - particles called baryons - that makes up stars, planets and
The 2dFGRS has shown that baryons are a small component of our Universe,
making up a mere 18% of the total mass. The remaining 82% is dark
For the first time, the 2dFGRS team have measured the density of matter
the Universe with an uncertainty of less than 10%.
Furthermore, the 2dFGRS has also shown that all the mass in the Universe
(both luminous and dark) is outweighed 4:1 by an even more exotic
called 'vacuum energy' or 'dark energy'. This has antigravity
causing the expansion of the Universe to speed up. This conclusion comes
from combining 2dFGRS results with data on the cosmic microwave
radiation. The origin and identity of the dark energy remains one of the
deepest mysteries of modern science.
Astronomers believe they could find clues to the identity of dark
identifying baryon wiggles in the pattern of galaxies that existed when
Universe was half its present age. They are now planning huge galaxy
to do this. "The Anglo-Australian Observatory has a radical new design
concept for an instrument to make such a mega-survey," said Dr Hawthorn.
The 2dF Instrument
Designed and built by the Anglo-Australian Observatory, the 2dF system
one of the world's most complex astronomical instruments, able to
400 spectra simultaneously. A robot arm positions up to 400 optical
on a field plate, each to within an accuracy of 20 micrometres. Light
up to 400 objects is collected and fed into two spectrographs for
The expansion of the Universe shifts galaxy spectra to longer
By measuring this 'redshift' in a galaxy's spectrum, the galaxy's
can be determined.
The 2dF Galaxy Redshift Survey used the 2dF system to cover a total
about 2,000 square degrees, selected from both northern and southern
It used about 250 nights observing time on the 3.9m-diameter
Anglo-Australian Telescope during 1995-2002.
The 2dF Galaxy Redshift Survey is nearly ten times larger than the
that preceded it.
2dF Galaxy Redshift Survey Team
Members of the team are based at the following institutions:
Anglo-Australian Observatory, The Australian National University,
Institute of Technology, CSIRO Australia Telescope National Facility,
Zurich, Johns Hopkins University, Liverpool John Moores University,
University, University of Bristol, University of Cambridge, University
College London, University of Durham, University of Edinburgh,
Leeds, University of New South Wales, University of Nottingham,
A paper on the finding, "The 2dF Galaxy Redshift Survey: Power-spectrum
analysis of the final dataset and cosmological implications", will be
on the astrophysics preprint server (Australian mirror site,
and will also be available at
It has been submitted to Monthly Notices of the Royal Astronomical
Society for publication.
A meeting to review the successes of 2dF will be held at the RAS on
13 and 14th. See http://www.ras.org.uk/html/meetings/RAS2004.html#jan
In the UK:
Dr Matthew Colless, Director, Anglo-Australian Observatory (Australian
leader of the 2dFGRS collaboration)
11 and 12 January
Day: Oxford University, Denys Wilkinson Building +44-1865-273-310
Evening: St Peter's College, Oxford +44-1865-278-900
Professor John Peacock, Institute for Astronomy, University of
team leader of the 2dFGRS collaboration)
+44-131-668-8100 (office) +44-7946-273-597 (mob.)
Dr Shaun Cole, Institute for Computational Cosmology,
Department of Physics, University of Durham (lead author for this
Dr Joss Hawthorn, Anglo-Australian Observatory
02-9960-6553 (home) 0404-858-054 (mob.)
Dr Russell Cannon, Anglo-Australian Observatory
02-9876-8117 (home) 0402-096-258 (mob.)
Dr Bruce Peterson, Research School of Astronomy and Astrophysics, The
Australian National University
02-6125-8035 (office) 0413-967-397 (mob.) 02-6231-2971 (home)
Dr Simon Driver, Research School of Astronomy and Astrophysics, The
Australian National University
02-6125-0222 (office) 02-6231-3120 (home)
Dr Warrick Couch, University of New South Wales
02-9385-4578 (office) 0413-011-371 (mob.)
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