Contact: Steve Roy
Media Relations Department
(256) 544-0034

Barbara Kennedy
Penn State Univ.
(814) 863-4682

Wallace Tucker
Chandra X-ray Observatory Center
(617) 496-7998

RELEASE: 00-162

Using NASA’s Chandra X-ray Observatory, astronomers have
made the first long-duration X-ray survey of the Hubble Deep
Field North. They detected X-rays from six of the galaxies in the
field, and were surprised by the lack of X-rays from some of the
most energetic galaxies in the field.

The X-ray emitting objects discovered by the research team are
a distant galaxy thought to contain a central giant black hole,
three elliptically shaped galaxies, an extremely red distant
galaxy, and a nearby spiral galaxy.

“We were expecting about five X-ray sources in this field,” said
Professor Niel Brandt of Pennsylvania State University,
University Park, and one of the leaders of the research team
that conducted the survey. “However, it was very surprising to
find that none of the X-ray sources lined up with any of the
submillimeter sources.”

The submillimeter sources are extremely luminous, dusty
galaxies that produce large amounts of infrared radiation.
Because they are over ten billion light years from Earth, their
infrared radiation is shifted to longer, submillimeter wavelengths
as it traverses the expanding universe. The primary source of
the large power of the submillimeter sources is thought to be an
unusually high rate of star formation, or the infall, or accretion of
matter into a giant black hole in the center of the galaxy. X-ray
observations provide the most direct measure of black hole
accretion power. X-rays, because of their high energy, would be
expected to pass through the gas and dust in these galaxies,
unlike visible light.

“With Chandra we have been able to place the best X-ray
constraints ever on submillimeter sources,” said Ann
Hornschemeier, also of Penn State, and the lead author of an
upcoming Astrophysical Journal paper describing the
discovery. “Our results indicate that less than 15 percent of the
submillimeter sources can be luminous X-ray sources.”

“That means,” Brandt explains, “Either there is an enormous
amount of star formation in those galaxies, or these objects
contain the best-hidden black holes in the universe.”

Chandra’s increased spatial resolution — the capability to
concentrate X-rays into a smaller area — also increases its
sensitivity for detecting fainter X-ray sources than ever before.
“Many of our sources are fainter than any source that was
detected in the deepest observations by all previous X-ray
observatories,” Hornschemeier says. The research team used
Chandra’s Advanced CCD Imaging Spectrometer (ACIS) to
make the unusually deep observation of the Hubble Deep Field
in X-rays for about 46 hours in November 1999.

The authors of the research paper titled “X-Ray Sources in the
Hubble Deep Field Detected by Chandra” are A. E.
Hornschemeier, W. N. Brandt, G. P. Garmire, D. P. Schneider,
P. S. Broos, L. K. Townsley, D. N. Burrows, E. D. Feigelson,
and J. A. Nousek at Penn State; M. W. Bautz at the
Massachusetts Institute of Technology,

Cambridge, Mass.; R. Griffiths at Carnegie Mellon University,
Pittsburgh, Penn.; D. Lumb at the European Space Research
and Technology Center in The Netherlands; and W. L. W.
Sargent at the California Institute of Technology, Pasadena,
Calif. The paper will be published in the September issue of the
Astrophysical Journal.

The ACIS X-ray camera was conceived and developed for
NASA by Penn State and the Massachusetts Institute of
Technology under the leadership of Gordon Garmire, Professor
of Astronomy and Astrophysics at Penn State.

NASA’s Marshall Space Flight Center in Huntsville, Ala.,
manages the Chandra program. TRW, Inc., Redondo Beach,
Calif., is the prime contractor for the spacecraft. The
Smithsonian’s Chandra X-ray Center controls science and flight
operations from Cambridge, Mass.

Images associated with this release are available on the World
Wide Web at:



Science Contacts:

Niel Brandt, 814-865-3509,
Ann E. Hornschemeier, 814-863-0182,