Astronomers surprised by 'STACKS' of Star-Making stuff near a Young Galaxy

Astronomers have discovered a massive reservoir of gas in a primeval galaxy, suggesting that large galaxies formed and began to fizz with stars earlier than was previously thought. Looking more than 12 billion years into the past, the scientists found that a quasar - the active central core in a young galaxy, powered by a black hole - is sitting next door to enough cold molecular gas to make 100 billion suns. The scientists report their findings in the 4 January issue of the journal "Nature".

The members of the research team are Padeli Papadoupoulos of Leiden Observatory in the Netherlands, Chris Carilli of the National Radio Astronomy Observatory in the USA, Rob Ivison of University College London in the UK and Geraint Lewis of the Anglo-Australian Observatory in Australia.

This is the first time anyone has seen the massive reservoir of cold gas needed for the frenzies of star formation called 'starbursts'. The gas is spread over a region roughly the size of our own Milky Way Galaxy.

"It's primed and ready to go," said Geraint Lewis. "If it could all turn into stars at once, we'd have an instant galaxy."

"We were shocked to see such a large gas cloud so early in the Universe's history."

Today's large galaxies are supposed to have been formed by smaller galaxies merging. "How a large gas cloud due to become a galaxy could have been formed so early is a bit of a mystery," said Geraint Lewis.

The astronomers found the gas while studying the quasar, called APM 08279+5255, which was discovered in 1998. The quasar has a redshift of 3.9, which means that it lies at a distance of about 12 billion light-years. We see the quasar as it was 12 billion years ago, just one or two billion years after the Big Bang and when the Universe was only a tenth of its present age.

"This thing is at the edge of the dark ages, before the first stars in the universe were born," said Chris Carilli.

The year after its discovery, APM 08279+5255 was found to have warm carbon monoxide (CO) gas near its centre, heated by the energy released as the black hole devours material. Observations with the Very Large Array radio telescope in New Mexico revealed cold CO gas much more widely distributed than its warmer counterpart. Based on observations of closer objects, the astronomers presume the CO gas is accompanied by large amounts of molecular hydrogen gas. Cold CO gas never has been detected before in such a distant object.

Although APM 08279+5255 is a young galaxy just starting its first massive burst of star formation, the CO gas indicates that some stars must have formed even earlier. Carbon and oxygen, the component elements of CO, are formed in the cores of stars. Their presence in the cold gas tells astronomers that a fleeting crop of extremely massive stars had been born, lived, then died in violent explosions (supernovae), spreading these elements throughout the galaxy's interstellar gas.

Paradoxically, the galaxy's great distance made it possible to discover the gas. The expansion of the universe 'stretches' light and radio waves to longer wavelengths - the more distant the object, the more stretching occurs. Radio waves emitted by the cold CO gas originally had wavelengths of about 1.3 and 2.6 millimetres, but were 'redshifted' to wavelengths of 7 and 13 millimetres, which the Very Large Array can receive.

The National Radio Astronomy Observatory is a facility of the US National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

For more information:

http://www.aao.gov.au/local/www/gfl/APM08
and images are available at
http://www.aao.gov.au/local/www/gfl/APM08/Images.html

Dr Geraint F. Lewis, Anglo-Australian Observatory, Sydney, Australia
+61-2-9372-4841 (work) +61-2-8850-5020 (home)
gfl@aaoepp.aao.gov.au

Dr Padeli Papadopoulos, Leiden Observatory, The Netherlands
+31-71-527-5852
papadop@strw.leidenuniv.nl

Dr Rob Ivison, University College London, U.K.
+44 (0)20 7679 3435
Mob +44 (0)7979 368142
rji@star.ucl.ac.uk

Dr Chris Carilli, National Radio Astronomy Observatory,
Socorro, U.S.A
+1 505 835 7000
ccarilli@nrao.edu