Galaxy patterns reveal missing link to Big Bang (Forwarded)

Anglo-Australian Observatory
Epping, Australia

CONTACTS

In the UK:

Dr Matthew Colless
Director, Anglo-Australian Observatory (Australian team 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 Edinburgh (UK team leader of the 2dFGRS
collaboration)
+44-131-668-8100 (office)


Dr Shaun Cole
Institute for Computational Cosmology
Department of Physics, University of Durham (lead author for this analysis)
+44-191-334-3593,

In Australia:

Dr Joss Hawthorn
Anglo-Australian Observatory


Dr Russell Cannon
Anglo-Australian Observatory


Dr Bruce Peterson
Research School of Astronomy and Astrophysics, The Australian National University
02-6125-8035 (office)


Dr Simon Driver
Research School of Astronomy and Astrophysics, The Australian National University
02-6125-0222 (office)


Dr Warrick Couch
University of New South Wales
02-9385-4578 (office)


Public Relations and Media Liaison
Helen Sim
CSIRO Australia Telescope National Facility

and Anglo-Australian Observatory

+61-2-9372-4261 (office)

NOTE: 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 Australian
National University, CSIRO and the University of New South Wales, together with
their UK colleagues, today announced that they have found the 'missing link'
that directly relates modern galaxies like our own Milky Way to the 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 space of
220,000 galaxies using the 3.9-m Anglo-Australian Telescope (AAT) in New South
Wales -- a project called the 2-degree Field Galaxy Redshift Survey (2dFGRS).

This survey was almost ten times larger than any previous such study.

It measured in detail patterns in the distribution of galaxies, on scales 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, Director of
the Anglo-Australian Observatory and Australian leader of the 2dFGRS team.
"Although there have been hints before of these features, this is the 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 amount of
mass for a given volume of space -- with an uncertainty of less than 10%."

"This survey, coupled with a few other lines of enquiry, has given us extremely
good measurements of two major constituents of the Universe -- its dark matter
and dark energy," said 2dFGRS team member Dr Warrick Couch of the University of
New South Wales.

Measuring the galaxies' distances and modelling their distribution in space had
taken "more than a decade of work" by a team of over 30 people, said Dr Bruce
Peterson of the ANU's Research School of Astronomy and Astrophysics, the 2dFGRS
team member who constructed the database for the survey.

Independent corroboration of the 2dFGRS result was also announced today by 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 of 46,000 highly
luminous red galaxies and a different method of analysis from the 2dFGRS team's.
"Happily, the two groups' conclusions are consistent," said 2dFGRS team member
Dr Joss Hawthorn of the Anglo-Australian Observatory.

The robotic 2dF instrument, which made the survey possible, was designed and
built by the Anglo-Australian Observatory. It measures the 'redshifts' of
galaxies -- a change in the light they emit that varies with distance, and which
can be used as a measure of distance. "The 2dF instrument is the world's most
efficient machine for measuring redshifts," said 2dFGRS team member Dr Russell
Cannon, a former director of the Anglo-Australian Observatory during whose term
the 2dFGRS had been initiated.

Matching ripples

Theorists in the 1960s suggested that the primordial seeds of galaxies should be
seen as 'ripples' -- a pattern of hotter and cooler spots -- in the cosmic
microwave background (CMB). This CMB is heat radiation left over from 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 satellite. But
until now, no-one had been able to definitely show how they were connected to
galaxy formation.

Astronomers use a statistic called the 'power spectrum' to mathematically
describe the pattern of spots in the CMB. A plot of the power spectrum has 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 power
spectrum of the CMB," said 2dFGRS team member Dr Simon Driver of the ANU's
Research School of Astronomy and Astrophysics. "This leaves no doubt that 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 about the
contents of the Universe; in particular about the amount of ordinary matter --
particles called baryons -- that makes up stars, planets and people.

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 matter. For the first
time, the 2dFGRS team have measured the density of matter in 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 component called
'vacuum energy' or 'dark energy'. This has antigravity properties, causing the
expansion of the Universe to speed up. This conclusion comes from combining
2dFGRS results with data on the cosmic microwave background 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 energy by
identifying baryon wiggles in the pattern of galaxies that existed when the
Universe was half its present age. They are now planning huge galaxy surveys 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.

NOTES

The 2dF Instrument

Designed and built by the Anglo-Australian Observatory, the 2dF system is one of
the world's most complex astronomical instruments, able to capture 400 spectra
simultaneously. A robot arm positions up to 400 optical fibres on a field plate,
each to within an accuracy of 20 micrometres. Light from up to 400 objects is
collected and fed into two spectrographs for analysis. The expansion of the
Universe shifts galaxy spectra to longer wavelengths. By measuring this
'redshift' in a galaxy's spectrum, the galaxy's distance can be determined.

The 2dF Galaxy Redshift Survey used the 2dF system to cover a total area of
about 2,000 square degrees, selected from both northern and southern skies. 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 surveys 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, California Institute of
Technology, CSIRO Australia Telescope National Facility, ETH Zurich, Johns
Hopkins University, Liverpool John Moores University, Queen's University,
University of Bristol, University of Cambridge, University College London,
University of Durham, University of Edinburgh, University of Leeds, University
of New South Wales, University of Nottingham, University of Oxford.

IMAGES

http://www.aao.gov.au/press/2dfgrs_wiggles.html

PUBLICATION

A paper on the finding, "The 2dF Galaxy Redshift Survey: Power-spectrum analysis
of the final dataset and cosmological implications", will be posted on the
astrophysics preprint server (Australian mirror site,
http://au.arxiv.org/archive/astro-ph), and will also be available at

http://www.mso.anu.edu.au/2dFGRS/Pub..._cosmology.pdf
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 January 13
and 14th. See
http://www.ras.org.uk/html/meetings/RAS2004.html#jan
for details.