New VLA Images Unlocking Galactic Mysteries (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 20 Jan 2008 18:33:50 GMT
National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu
Contact:
Dave Finley, Public Information Officer
(505) 835-7302
EMBARGOED For Release: 9:30 a.m., CST, Thursday, January 10, 2008
New VLA Images Unlocking Galactic Mysteries
Astronomers have produced a scientific gold mine of detailed, high-quality
images of nearby galaxies that is yielding important new insights into
many aspects of galaxies, including their complex structures, how they
form stars, the motions of gas in the galaxies, the relationship of
"normal" matter to unseen "dark matter," and many others.
An international team of scientists used more than 500 hours of
observations with the National Science Foundation's Very Large Array (VLA)
radio telescope to produce detailed sets of images of 34 galaxies at
distances from 6 to 50 million light-years from Earth. Their project,
called The HI Nearby Galaxy Survey, or THINGS, required two years to
produce nearly one TeraByte of data. HI ("H-one") is an astronomical term
for atomic hydrogen gas. The astronomers presented their initial findings
to the American Astronomical Society's (AAS) meeting in Austin, Texas.
"Studying the radio waves emitted by atomic hydrogen gas in galaxies is an
extremely powerful way to learn what's going on in nearby galaxies. The
THINGS survey uses that tool to provide sets of images of the highest
quality and sensitivity for a substantial sample of galaxies of different
types," said Fabian Walter, of the Max-Planck Institute for Astronomy in
Heidelberg, Germany.
Most of the galaxies studied in the THINGS survey also have been observed
at other wavelengths, including Spitzer space telescope infrared images
and GALEX ultraviolet images. This combination provides an unprecedented
resource for unravelling the mystery of how a galaxy's gaseous material
influences its overall evolution.
Analysis of THINGS data already has yielded numerous scientific payoffs.
For example, one study has shed new light on astronomers' understanding of
the gas-density threshold required to start the process of star formation.
"Using the data from THINGS in combination with observations from NASA's
space telescopes has allowed us to investigate how the processes leading
to star formation differ in big spiral galaxies like our own and much
smaller, dwarf galaxies," said Adam Leroy and Frank Bigiel of the
Max-Planck Insitute for Astronomy at the Austin AAS meeting.
Because atomic hydrogen emits radio waves at a specific frequency,
astronomers can measure motions of the gas by noting the Doppler shift in
frequency caused by those motions. "Because the THINGS images are highly
detailed, we have been able to measure both the rotational motion of the
galaxies and non-circular random motions within the galaxies," noted Erwin
de Blok of the University of Cape Town, South Africa.
The motion measurements are providing new information about the
mysterious, unseen "dark matter" in the galaxies. "The non-circular
motions revealed by the THINGS observations, turn out to be too small to
solve a long-standing problem in cosmology, namely the inability of
state-of-the-art computer simulations to describe the distribution of dark
matter in disk galaxies. It was thought that random motions could explain
that inability, but our data show otherwise," de Blok explained.
The THINGS images revealed what Elias Brinks of the University of
Hertfordshire, UK, called a "stunning complexity of structures in the
tenuous interstellar medium of the galaxies." These structures include
large shells and "bubbles," presumably caused by multiple supernova
explosions of massive stars. Analyzing the detail of these complex
structures will help astronomers better understand the differences in star
formation processes in the varied types of galaxies.
Even such a simple question such as how big are the disks of gas in spiral
galaxies had largely eluded astronomers previously. "The quality and
sensitivity of the THINGS images has allowed us to see the actual edges of
these disks in a large sample of galaxies," said Brinks.
The new survey also showed a fundamental difference between the nearby
galaxies -- part of the "current" Universe, and far more distant galaxies,
seen as they were when the Universe was much younger. "It appears that the
gas in the galaxies in the early Universe is much more 'stirred up,'
possibly because galaxies were colliding more frequently then and there
was more intense star formation causing material outflows and stellar
winds," explained Martin Zwaan of the European Southern Observatory. The
information about gas in the more distant galaxies came through
non-imaging analysis.
These discoveries, the scientists predict, are only the tip of the
iceberg. "This survey produced a huge amount of data, and we've only
analyzed a small part of it so far. Further work is sure to tell us much
more about galaxies and how they evolve. We expect to be surprised,"
Walter said. In addition to the presentations made at the Austin AAS
meeting, THINGS team members also have submitted a series of scientific
papers to the Astronomical Journal.
The THINGS project is a large international collaboration led by Walter
and includes research teams led by Brinks, de Blok, Michele Thornley of
the Bucknell University in the U.S. and Rob Kennicutt of the Cambridge
University in the UK.
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/2008/things/ ]
.
- Prev by Date: Gliese 581: one planet might indeed be habitable (Forwarded)
- Next by Date: New Hydrogen Clouds in the M81 Group of Galaxies (Forwarded)
- Previous by thread: Gliese 581: one planet might indeed be habitable (Forwarded)
- Next by thread: New VLA Images Unlocking Galactic Mysteries (Forwarded)
- Index(es):
Relevant Pages
|
|
