Astronomers Discover Most Distant Galaxy Showing Key Evidence ForFurious Star Formation (Forwarded)

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Astronomers Discover Most Distant Galaxy Showing Key Evidence For Furious Star
Formation

Astronomers have discovered a key signpost of rapid star formation in a galaxy
11 billion light-years from Earth, seen as it was when the Universe was only 20
percent of its current age. Using the National Science Foundation's Very Large
Array (VLA) radio telescope, the scientists found a huge quantity of dense
interstellar gas -- the environment required for active star formation -- at the
greatest distance yet detected.

A furious spawning of the equivalent of 1,000 Suns per year in a distant galaxy
dubbed the Cloverleaf may be typical of galaxies in the early Universe, the
scientists say.

"This is a rate of star formation more than 300 times greater than that in our
own Milky Way and similar spiral galaxies, and our discovery may provide
important information about the formation and evolution of galaxies throughout
the Universe," said Philip Solomon, of Stony Brook University in New York.

While the raw material for star formation has been found in galaxies at even
greater distances, the Cloverleaf is by far the most distant galaxy showing this
essential signature of star formation. That essential signature comes in the
form of a specific frequency of radio waves emitted by molecules of the gas
hydrogen cyanide (HCN).

"If you see HCN, you are seeing gas with the high density required to form
stars," said Paul Vanden Bout of the National Radio Astronomy Observatory (NRAO).

Solomon and Vanden Bout worked with Chris Carilli of NRAO and Michel Guelin of
the Institute for Millimeter Astronomy in France. They reported their results in
the December 11 issue of the scientific journal Nature.

In galaxies like the Milky Way, dense gas traced by HCN but composed mainly of
hydrogen molecules is always associated with regions of active star formation.
What is different about the Cloverleaf is the huge quantity of dense gas along
with very powerful infrared radiation from the star formation. Ten billion times
the mass of the Sun is contained in dense, star-forming gas clouds.

"At the rate this galaxy is seen to be forming stars, that dense gas will be
used up in only about 10 million years," Solomon said.

In addition to giving astronomers a fascinating glimpse of a huge burst of star
formation in the early Universe, the new information about the Cloverleaf helps
answer a longstanding question about bright galaxies of that era. Many distant
galaxies have supermassive black holes at their cores, and those black holes
power "central engines" that produce bright emission. Astronomers have wondered
specifically about those distant galaxies that emit large amounts of infrared
light, galaxies like the Cloverleaf which has a black hole and central engine.

"Is this bright infrared light caused by the black-hole-powered core of the
galaxy or by a huge burst of star formation? That has been the question. Now we
know that, in at least one case, much of the infrared light is produced by
intense star formation," Carilli said.

The rapid star formation, called a starburst, and the black hole are both
generating the bright infrared light in the Cloverleaf. The starburst is a major
event in the formation and evolution of this galaxy.

"This detection of HCN gives us a unique new window through which we can study
star formation in the early Universe," Carilli said.

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

[NOTE: Images supporting this release are available at
http://www.nrao.edu/pr/2003/cloverle...f.images.shtml ]