Sky Survey Provides New Radio View of Universe (Forwarded)

National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu

Contact:
Dave Finley, Public Information Officer, Socorro, NM
(505) 835-7302,

October 20, 2004

Sky Survey Provides New Radio View of Universe

Astronomers using the National Science Foundation's Very Large Array (VLA) have
overcome longstanding technical hurdles to map the sky at little-explored radio
frequencies that may provide a tantalizing look deep into the early Universe.
The scientists have released images and data covering half of the sky visible
from the VLA, and hope to complete their survey within a year.

The VLA Low-frequency Sky Survey (VLSS) [ http://lwa.nrl.navy.mil/VLSS/ ] is
producing sky images made at an observing frequency of 74 MHz, a far lower
frequency than used for most current radio-astronomy research.

"Because of the Earth's ionosphere, such a low frequency has proven very
difficult for high-quality imaging, and it is only in the past few years that we
have developed the techniques that make a project like the VLSS possible," said
Rick Perley, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM.

Because the high-quality VLSS images will give astronomers a look at the
Universe through what essentially is a new "window," they expect the images to
reveal some rare and important objects.

"We expect to find very distant radio galaxies -- galaxies spewing jets of
material at nearly light speed and powered by supermassive black holes," said
Joseph Lazio of the Naval Research Laboratory in Washington, DC. "By determining
just how distant these radio galaxies are, we will learn how early the black
holes formed in the history of the Universe," he added.

Another tantalizing possibility is that the low-frequency images may reveal
"halos" and "relics" produced by collisions of galaxies in clusters. If the
halos and relics are found in the distant, and thus early, Universe, it will
give scientists important clues about the timetable for formation of large-scale
structure. In addition, the astronomers hope that the VLSS images may show
previously-undiscovered pulsars -- superdense, spinning neutron stars.

Massive planets -- "super Jupiters" circling stars beyond the Sun -- also might
reveal themselves through bursts of radio emission at the frequency of this
survey, the astronomers speculated.

Images from the survey are being made available to other scientists as soon as
they are completed. The survey will use some 800 hours of VLA observing time.
The newly-released images and data are available via the NRAO Web site,
http://www.nrao.edu/astrores/

"By doing this survey and making the results available, we are bringing
low-frequency radio data, previously quite difficult to produce, to all
astronomers in a simple and easy manner," Perley said.

"We also expect that this survey will spur additional research into objects that
scientists find puzzling or interesting," Perley saidd. "We really will have to
wait for years to know the full scientific benefit of this survey," he said.

In addition to Perley and Lazio, the VLSS team includes James Condon and William
Cotton of NRAO; Aaron Cohen and Wendy Lane of the National Research Council and
the Naval Research Laboratory; Namir Kassim of the Naval Research Laboratory;
and William Erickson of the University of Maryland and University of Tasmania.

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/2004/vlss/vlss.graphics.shtml ]