Andrew Yee[_1_]
January 11th 08, 02:48 AM
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/ ]
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/ ]