Astronomers Eye Ultra-Young, Bright Galaxy in Early Universe

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Rosemary Sullivant 818-354-2274 Rosemary.Sullivant@jpl.nasa.gov
Jet Propulsion Laboratory, Pasadena, Calif.

Donna Weaver/Ray Villard 410-338-4493/4514 dweaver@stsci.edu/villard@stsci.edu
Space Telescope Science Institute, Baltimore, Md.

NEWS RELEASE: 2008-024 Feb. 12, 2008

Astronomers Eye Ultra-Young, Bright Galaxy in Early Universe

NASA's Hubble and Spitzer space telescopes, with a boost from a natural "zoom lens,"
have uncovered what may be one of the youngest and brightest galaxies ever seen in the
middle of the cosmic "dark ages," just 700 million years after the beginning of our
universe.

The detailed images from Hubble's Near Infrared Camera and Multi-Object Spectrometer
reveal an infant galaxy, dubbed A1689-zD1, undergoing a firestorm of star birth during
the dark ages, a time shortly after the Big Bang but before the first stars reheated the cold,
dark universe. Images from NASA's Spitzer Space Telescope's Infrared Array Camera
provided strong additional evidence that it was a young star-forming galaxy in the dark
ages.

"We certainly were surprised to find such a bright young galaxy 12.8 billion years in the
past," said astronomer Garth Illingworth of the University of California, Santa Cruz, and
a member of the research team. "This is the most detailed look to date at an object so far
back in time."

"The Hubble images yield insight into the galaxy's structure that we cannot get with any
other telescope," added astronomer Rychard Bouwens of UC Santa Cruz, a co-discoverer.
The new images should offer insights into the formative years of galaxy birth and
evolution and yield information on the types of objects that may have contributed to
ending the dark ages. The faraway galaxy also is an ideal target for Hubble's successor,
the James Webb Space Telescope, scheduled to launch in 2013.

During its lifetime, the Hubble telescope has peered ever farther back in time, viewing
galaxies at successively younger stages of evolution. These snapshots have helped
astronomers create a scrapbook of galaxies from infancy to adulthood. The new Hubble
and Spitzer images of A1689-zD1 show a time when galaxies were in their infancy.

Current theory holds that the dark ages began about 400,000 years after the Big Bang, as
matter in the expanding universe cooled and formed clouds of cold hydrogen. These cold
clouds pervaded the universe like a thick fog. At some point during this era, stars and
galaxies started to form. Their collective light reheated the foggy, cold hydrogen, ending
the dark ages about a billion years after the Big Bang.

"This galaxy presumably is one of the many galaxies that helped end the dark ages," said
astronomer Larry Bradley of Johns Hopkins University in Baltimore, Md., and leader of
the study. "Astronomers are fairly certain that high-energy objects such as quasars did not
provide enough energy to end the dark ages of the universe. But many young star-
forming galaxies may have produced enough energy to end it."

The galaxy is so far away it did not appear in images taken with Hubble's Advanced
Camera for Surveys, because its light is stretched to invisible infrared wavelengths by the
universe's expansion. It took Hubble's near infrared camera/spectrometer, Spitzer, and a
trick of nature called gravitational lensing to see the faraway galaxy. The astronomers
used a relatively nearby massive cluster of galaxies known as Abell 1689, roughly 2.2
billion light-years away, to magnify the light from the more distant galaxy directly behind
it. This natural telescope is called a gravitational lens.

Though the diffuse light of the faraway object is nearly impossible to see, gravitational
lensing has increased its brightness by nearly 10 times, making it bright enough for
Hubble and Spitzer to detect. A telltale sign of the lensing is the smearing of the images
of galaxies behind Abell 1689 into arcs by the gravitational warping of space by the
intervening galaxy cluster.

The images reveal bright, dense clumps of hundreds of millions of massive stars in a
compact region about 2,000 light-years across, which is only a fraction of the width of
our Milky Way Galaxy. This type of galaxy is not uncommon in the early universe, when
the bulk of star formation was taking place, Bradley and Illingworth said.

Spitzer's images show the galaxy's mass is typical of galaxies in the early universe. Its
mass is equivalent to several billions of sunlike stars, or just a tiny fraction of the mass of
the Milky Way. "This observation confirms previous Hubble studies that star birth
happens in very tiny regions compared with the size of the final galaxy," Illingworth said.

Even with the increased magnification from the gravitational lens, Hubble's sharp "eye"
can only see knots of the brightest, heftiest stars in the galaxy. The telescope cannot
pinpoint fainter, lower-mass stars, individual stars, or the material surrounding the star-
birthing region. To see those things, astronomers will need the infrared capabilities of
the Webb Telescope. The planned infrared observatory will have a mirror about seven
times the area of Hubble's primary mirror and will collect more light from faint galaxies.
It also will be able to view even more remote galaxies whose light has been stretched
deep into infrared wavelengths that are out of the reach of Hubble.

Team member Holland Ford of Johns Hopkins University said this galaxy will be one of
the first objects the Webb Telescope will observe, saying, "This object is a pathfinder for
the James Webb Space Telescope for deciphering what is happening in young galaxies."
The astronomers noted that the faraway galaxy also would be an ideal target for the
Atacama Large Millimeter Array, which, when completed in 2012, will be the world's
most powerful radio telescope.

The results will appear in the Astrophysical Journal, with followup observations planned
with Hawaii's Keck telescope. Images and additional information are at

http://spitzer.caltech.edu/media/mediaimages/index.shtml and

http://hubblesite.org/news/2008/08 . More information about Spitzer is at

http://www.nasa.gov/spitzer and http://www.spitzer.caltech.edu/spitzer .

The Space Telescope Science Institute conducts science operations for Hubble, a project
of international cooperation between NASA and the European Space Agency. The
institute is operated for NASA by the Association of Universities for Research in
Astronomy, Inc., Washington. The Jet Propulsion Laboratory, Pasadena, Calif., manages
Spitzer for NASA's Science Mission Directorate. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology, which manages JPL for
NASA. More contacts: Larry Bradley-Johns Hopkins University, Baltimore, 410-516-
5108/Garth Ilingworth-UC Observatories/UC Santa Cruz , 831-459-2843

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