NASA Telescopes Help Identify Most Distant Galaxy Cluster

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Whitney Clavin 818-354-4673
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Trent Perrotto 202-358-0321
NASA Headquarters, Washington
trent.j.perrotto@nasa.gov

NEWS RELEASE: 2011-013 Jan. 12, 2011

NASA Telescopes Help Identify Most Distant Galaxy Cluster

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-013&cid=release_2011-013

PASADENA, Calif. -- Astronomers have uncovered a burgeoning
galactic metropolis, the most distant known in the early universe. This
ancient collection of galaxies presumably grew into a modern galaxy
cluster similar to the massive ones seen today.

The developing cluster, named COSMOS-AzTEC3, was discovered
and characterized by multi-wavelength telescopes, including NASA's
Spitzer, Chandra and Hubble space telescopes, and the ground-based
W.M. Keck Observatory and Japan's Subaru Telescope.

"This exciting discovery showcases the exceptional science made
possible through collaboration among NASA projects and our
international partners," said Jon Morse, NASA's Astrophysics Division
director at NASA Headquarters in Washington.

Scientists refer to this growing lump of galaxies as a proto-cluster.
COSMOS-AzTEC3 is the most distant massive proto-cluster known,
and also one of the youngest, because it is being seen when the
universe itself was young. The cluster is roughly 12.6 billion light-
years away from Earth. Our universe is estimated to be 13.7 billion
years old. Previously, more mature versions of these clusters had been
spotted at 10 billion light-years away.

The astronomers also found that this cluster is buzzing with extreme
bursts of star formation and one enormous feeding black hole.

"We think the starbursts and black holes are the seeds of the cluster,"
said Peter Capak of NASA's Spitzer Science Center at the California
Institute of Technology in Pasadena. "These seeds will eventually grow
into a giant, central galaxy that will dominate the cluster -- a trait found
in modern-day galaxy clusters." Capak is first author of a paper
appearing in the Jan. 13 issue of the journal Nature.

Most galaxies in our universe are bound together into clusters that dot
the cosmic landscape like urban sprawls, usually centered around one
old, monstrous galaxy containing a massive black hole. Astronomers
thought that primitive versions of these clusters, still forming and
clumping together, should exist in the early universe. But locating one
proved difficult—until now.

Capak and his colleagues first used the Chandra X-ray Observatory and
the United Kingdom's James Clerk Maxwell Telescope on Mauna Kea,
Hawaii, to search for the black holes and bursts of star formation
needed to form the massive galaxies at the centers of modern galaxy
cities. The astronomers then used the Hubble and Subaru telescopes to
estimate the distances to these objects, and look for higher densities of
galaxies around them. Finally, the Keck telescope was used to confirm
that these galaxies were at the same distance and part of the same
galactic sprawl.

Once the scientists found this lumping of galaxies, they measured the
combined mass with the help of Spitzer. At this distance, the optical
light from stars is shifted, or stretched, to infrared wavelengths that can
only be observed in outer space by Spitzer. The lump sum of the mass
turned out to be a minimum of 400 billion suns -- enough to indicate
that the astronomers had indeed uncovered a massive proto-cluster.
The Spitzer observations also helped confirm that a massive galaxy at
the center of the cluster was forming stars at an impressive rate.

Chandra X-ray observations were used to find and characterize the
whopping black hole with a mass of more than 30 million suns.
Massive black holes are common in present-day galaxy clusters, but
this is the first time a feeding black hole of this heft has been linked to
a cluster that is so young.

Finally, the Institut de Radioastronomie Millimétrique's interferometer
telescope in France and 30-meter (about 100-foot) telescope in Spain,
along with the National Radio Astronomy Observatory's Very Large
Array telescope in New Mexico, measured the amount of gas, or fuel
for future star formation, in the cluster. The results indicate the cluster
will keep growing into a modern city of galaxies.

"It really did take a village of telescopes to nail this cluster," said
Capak. "Observations across the electromagnetic spectrum, from X-ray
to millimeter wavelengths, were all critical in providing a
comprehensive view of the cluster's many facets."

COSMOS-AzTEC3, located in the constellation Sextans, is named
after the region where it was found, called COSMOS after the Cosmic
Evolution Survey. AzTEC is the name of the camera used on the James
Clerk Maxwell Telescope; this camera is now on its way to the Large
Millimeter Telescope located in Mexico's Puebla state.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the
Spitzer Space Telescope mission for NASA's Science Mission
Directorate, Washington. Science operations are conducted at the
Spitzer Science Center at Caltech in Pasadena. Caltech manages JPL for
NASA. More information about Spitzer is at:
http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

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