Cosmic Beacons Trace The Map Of Creation

SPACE SCIENCE

A distribution of quasars from the 2dF survey. Our galaxy is situated at the centre of the plot. Each point represents a quasar. The low density radial strips are regions which are yet to be observed. With the 2dF survey we can detect quasars to distances of about 14 billion light years. Image by Anglo-Australian Observatory. Full size image

Sydney - April 3 2001
The structure of our Universe has been mapped out to a distance of 14 billion light-years -- almost as far as we can see -- by astronomers who have observed 11,000 quasars with the Anglo-Australian Telescope in eastern Australia, in the largest quasar redshift survey to date.

The structure is much lumpier at large scales than anyone predicted. The findings will be presented simultaneously on Wednesday 4 April by Dr. Robert Smith of Liverpool John Moores University at the UK National Astronomy Meeting in Cambridge, UK, and by Professor Tom Shanks of the University of Durham at 'The Dark Universe' symposium at the Space Telescope Science Institute, Baltimore, USA.

"The lumpiness we see at very large-scales must be almost entirely determined by the conditions in the fireball of the Big Bang during the first second of the Universe's life," said Professor Shanks, co-leader of the two-degree field (2dF) quasar survey.

"For this reason, we can say that the survey quasars are truly tracing the map of creation."

Cosmological models that predict less lumpiness at large scales are in trouble, said Dr. Smith.

"These include some of the standard cosmological models with lots of 'dark matter' built in," he said.

Quasars are the bright cores of distant galaxies. They make exceptionally luminous 'cosmic beacons' that can be easily seen out to a distance of 10 billion light-years, much further than galaxies.

The unprecedented size of the 2dF survey means it can capture structure on scales of up to 1000 million light-years, which has never been possible before.

"Imagine the Universe is a room. Previous surveys have involved peering through the keyhole to try to make out the pattern of the wallpaper," said Professor Brian Boyle, survey co-leader and Director of the Anglo-Australian Observatory. "Now we've opened the door at least a chink."

Averaged over the whole volume of the survey, the quasars are clustered to the same extent as local, optically selected galaxies -- a result previously only hinted at.

Because light takes a long time to travel vast distances, the most distant quasars we can see existed early in the history of the Universe -- 14 billion years ago.

"As far back as we look in this survey, we see the same strength of quasar clustering," said 2dF team member Dr Scott Croom of the Anglo-Australian Observatory.

"Imagine that the quasars are streetlights, marking out the structure of a city such as New York. It's as if we visited the city when it was still a Dutch colony, yet found the same road pattern that exists today."

The first instalment of data from the two-degree (2dF) quasar survey will be released to the world-wide astronomical community this week. Now 60% complete, the survey has already netted more quasars than were previously known. When finished in 2002 it will have measured the redshifts of 25,000 quasars -- fifty times more than the largest previous survey.

The completed survey will allow many new cosmological studies, including measurements of the Universal space curvature by foreground galaxies 'gravitationally lensing' the light from background quasars.

The members of the 2dF quasar survey team are: Professor Brian Boyle, Anglo-Australian Observatory; Professor Tom Shanks, University of Durham; Dr Lance Miller, University of Oxford; Dr Scott Croom, Anglo-Australian Observatory; Ms Nicola Loaring, University of Oxford; Dr Robert Smith, Liverpool John Moores University; Dr. Fiona Hoyle, Drexel University; and Dr. Phil Outram, University of Durham.

SPACE SCIENCE

Universe Weighed and 'Found Wanting'

Coonabarabran - March 8, 2001
Only 35% of the Universe's contents is in the form of matter, according to findings published in the journal Nature today [8 March] by astronomers using the Anglo-Australian Telescope near Coonabarabran in eastern Australia. The rest is believed to be in the form of 'dark energy'.

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