The most distant X-ray cluster of galaxies yet has been found by
astronomers using NASA’s Chandra X-ray Observatory. Approximately 10
billion light-years from Earth, the cluster 3C294 is 40 percent farther than
the next most distant X-ray galaxy cluster. The existence of such a distant
galaxy cluster is important for understanding how the universe evolved.
“Distant objects like 3C294 provide snapshots to how these galaxy
clusters looked billions of years ago,” said Andrew Fabian of the Institute
of Astronomy, Cambridge, England and lead author of the paper accepted for
publication in the Monthly Notices of Britain’s Royal Astronomical Society.
“These latest results help us better understand what the Universe was like
when it was only 20 percent of its current age.”
Chandra’s image reveals an hourglass-shaped region of X-ray emission
centered on the previously known central radio source. This X-ray emission
extends outward from the central galaxy for at least 300,000 light years and
shows that the known radio source is in the central galaxy of a massive
cluster.
Scientists have long suspected that distant radio-emitting galaxies
like 3C294 are part of larger groups of galaxies known as “clusters.”
However, radio data provides astronomers with only a partial picture of
these distant objects.
Confirmation of the existence of clusters at great distances – and,
hence, at early stages of the Universe – requires information from other
wavelengths. Optical observations can be used to pinpoint individual
galaxies, but X-ray data are needed to detect the hot gas that fills the
space within the cluster.
“Galaxy clusters are the largest gravitationally bound structures in
the Universe,” said Fabian. “We do not expect to find many massive objects,
such as the 3C294 cluster, in early times because structure is thought to
grow from small scales to large scales.”
The vast clouds of hot gas that envelope galaxies in clusters are
thought to be heated by collapse toward the center of the cluster. Until
Chandra, X-ray telescopes have not had the needed sensitivity to identify
and measure hot gas clouds in distant clusters. Carolin Crawford, Stefano
Ettori and Jeremy Sanders of the Institute of Astronomy were also members of
the team that observed 3C294 for 5.4 hours on October 29, 2000 with the
Advanced CCD Imaging Spectrometer (ACIS).
The ACIS X-ray camera was developed for NASA by Pennsylvania State
University and Massachusetts Institute of Technology. NASA’s Marshall Space
Flight Center in Huntsville, Ala., manages the Chandra program for the
Office of Space Science in Washington, DC. The Smithsonian’s Chandra X-ray
Center controls science and flight operations from Cambridge, Mass.
Images associated with the release are available at:
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