AUSSIES HELP HUBBLE HUNT ANCIENT GALAXIES

The Anglo-Australian Observatory and CSIRO helped choose the patch of sky in which the HST found the previously unknown galaxies. They are now helping Hubble astronomers to learn more about these new discoveries.

Preliminary HST results were released today by NASA's Space Telescope Science Institute, as were the results from the Australian institutions.

The piece of sky is tiny, the size of an echidna's eye on a five-cent piece held at arm's length. Called the Hubble Deep Field South , it complements the original Hubble Deep Field , another small patch in the northern sky.

Hubble Deep Field South (HDF-S)

The HST wowed the scientific world when in late 1995 it stared at the apparently blank piece of sky and found in it remarkable distant fossil galaxies, some formed when the Universe was only a tenth of its present age.

This time around astronomers wanted a piece of sky with a distant quasar (a galaxy with an extremely bright centre) in it. The quasar lights up and makes visible any material in space between it and the Earth, like a car headlight shining through fog at night.

Astronomers of the Anglo-Australian Observatory in Sydney, aided by their colleagues in Cambridge, UK, painstakingly sifted through their photographic records of the whole southern sky until they found a likely quasar, 10 billion light-years distant. The Anglo-Australian Telescope was used to confirm that the quasar was suitable. CSIRO's Australia Telescope was used to check that there were not too many confusing radio sources in the field.

The Hubble Space Telescope spent ten days in October scrutinising the new patch of sky.

Every major telescope that can see the Deep Field South has also made observations of the field and is releasing them to the astronomical community at the same time as the HST results come out.

"This is a new way of working," said Dr Ray Norris, head of Astrophysics at CSIRO's Australia Telescope National Facility. "Everyone is putting their data on the Web, warts and all. The galaxies in this field are being studied incredibly intensively, with optical, radio, infrared and UV observations all being made at more or less at the same time."

"We currently each have one piece of the jigsaw puzzle which will be put together to reveal a new picture of the distant Universe," said Dr Brian Boyle, Director of the Anglo-Australian Observatory.

The Anglo-Australian Telescope has measured the distances of about 75 faint far-flung galaxies in the field.

"These distances can be combined with other information to produce a 3D map of this part of the Universe," explained Dr Boyle.

"Those galaxies for which we have the distances are all young -'newborns', so to speak," he said. "The gas clouds that are lit up by the quasar are probably forming galaxies - embryos. We want to compare the two kinds, to build up a picture of the life cycle of galaxies from creation through to old age."

The radio telescope observations are proving more mysterious.

"We have already found one extremely puzzling object," said Dr Norris. "We don't know what it is."

"It could be a very distant version of a kind of galaxy we know about, called a starburst galaxy, obscured by dust. But to be at that distance and still look so big, it would have to be enormous. On the other hand, we really don't know what to expect from galaxies at that distance."

Astronomers overhauled their theories of how galaxies evolve and how fast stars form after studying the 'core-sample' of galaxies dredged up by the original Hubble Deep Field. Now the Hubble Deep Field South will show if the original Hubble Deep Field North was truly a representative patch of the Universe.

"It will take astronomers months to digest all this new data," predicted Dr Boyle.

More information:

Dr Ray Norris, CSIRO
Tel: (02) 9372 4416 (bh), (02) 9369 9591 (ah), 0417 288 307 (mobile)
E-mail: rnorris@atnf.csiro.au

Dr Brian Boyle, Anglo-Australian Observatory
Tel: (02) 9372 4811 (bh), (02) 9498 1584 (ah)
E-mail: director@aaoepp.aao.gov.au

Hubble Space Telescope

http://oposite.stsci.edu/pubinfo/1998/41
http://oposite.stsci.edu/pubinfo/pictures.html

CSIRO Australia Telescope National Facility

http://www.atnf.csiro.au/~rnorris/hdf-s

Anglo-Australian Observatory

http://local.aao.gov.au/AAO/hdfs/

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