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Astronomers find massive gas cloud near young galaxy

Posted: January 4, 2000

A massive gas cloud with the raw materials to form 100 billion stars could reshape theories of galaxy formation, astronomers said this week.

In a paper published in Thursday's issue of the journal Nature, an international team of astronomers said a distant young galaxy harbors a unexpectedly massive cloud of hydrogen gas that may fuel a burst of star formation.

The quasar APM 08279+5255 burns brightly in the lower right hand corner, while the ghostly gas cloud floats nearby as seen in this rendering. Credit: Geraint Lewis
The cloud was discovered by radio observations of APM 08279+5255, a quasar located 12 billion light-years from the Earth. First discovered in 1998, the quasar has since been resolved by optical and infrared telescopes to be a young, forming galaxy with a powerful black hole at its core and a burst of star formation taking place. Astronomers used the Very Large Array (VLA) to look for evidence of carbon monoxide (CO), a gas that acts as a tracer for the more plentiful, but harder to detect, hydrogen.

Astronomers detected, as expected, traces of warm CO near the black hole. However, the VLA data also showed evidence for a much larger amount of colder CO in a wider area some distance from the quasar. Based on observations of nearer objects, astronomers concluded that the cloud also contains a massive amount of hydrogen: enough, they calculate, to create 100 billion stars, enough to populate an entire galaxy.

"This is the first time anyone has seen the massive reservoir of cold gas required for these incredible 'starbursts' to produce a galaxy," said Chris Carilli, an astronomer with the National Radio Astronomy Observatory and one of the co-authors of the Nature paper. "There is much more gas here than we anticipated."

Dust emission from APM 08279+5255. Credit: Geraint Lewis

That large amount of gas could force astronomers to revisit existing explanations for galaxy formation. Astronomers generally believe that galaxies are built up gradually, as smaller bodies created early in the history of the Universe collide and coalesce to form the larger objects, containing hundreds of billions of stars, seen today. However, astronomers see enough gas in this distant object for a full-fledged galaxy to form even though the observations of the object date back to when the Universe was only about a billion years old.

"Such 'ready made' galaxies should not exist at the early epoch of the Universe," the astronomers note in a document published on their web site, "and hence our discovery is currently at odds with our understanding of the growth and evolution of structure in the Universe."

"This new result is a crucial piece in the jigsaw and may help resolve many misconceptions about how galaxies form and evolve," said Rob Ivison, an astronomer at University College London.

The discovery of the CO means that one generation of stars has already lived and died in the young galaxy. Carbon and oxygen are formed in the cores of supermassive stars that live for only a few million years before dying in powerful supernova explosions. Those supernovae distribute the elements into the gas cloud, where they form carbon monoxide.

"It took eight years to refine this technique, but the effort has been worthwhile," Ivison said. "This is the golden age of cosmology. We are learning more and more about our universe, from the smallest planets to the largest galaxy clusters."