Andrew Yee[_1_]
January 8th 08, 10:21 PM
Office of Public Relations
University of Alabama
Tuscaloosa, Alabama
Contact:
Chris Bryant
University of Alabama Assistant Director of Media Relations
205/348-8323
Sources:
Dr. Gene Byrd
Department of physics and astronomy, University of Alabama
205/394-5853
Tarsh Freeman
Department of mathematics, Bevill Community College
800/648-3271, ext. 5167
Dr. Ron Buta
Department of physics and astronomy, University of Alabama
205/348-3792
Dr. Sethanne Howard
Columbia Md.
January 8, 2007
UA Astronomers on Team Describing New Evidence of 'Inconvenient' Galaxy
TUSCALOOSA, Ala. -- Discovery of two new components within a puzzling spiral
galaxy confirm it must have a pair of arms winding in the opposite direction
from most galaxies, according to results being presented today to the
American Astronomical Society meeting in Austin, Texas. Presenting the
results are Drs. Gene Byrd and Ron Buta, from The University of Alabama;
Tarsh Freeman, Bevill Community College; and Dr. Sethanne Howard, retired
from the U.S. Naval Observatory.
"While the existence of a galaxy with a pair of 'backward' arms may seem
like an inconvenient truth to many, our latest analysis indicates it is,
nonetheless, a reality," says Byrd, professor of astronomy at The University
of Alabama.
The galaxy, known as NGC4622, lies 200 million light years away in the
constellation Centaurus.
Spiral arm pairs seen in galaxies are thought to trail, meaning they wind
outward, opposite the direction of rotation of the disk material. Leading
arms, such as the pair reported by the astronomers for NGC4622, do the
opposite, opening outward in the same direction as the rotation of the
galaxy's disk.
Using a Fourier component image method to further analyze a 2001 Hubble
Space Telescope image, the team discovered a previously hidden inner counter
clockwise pair of spiral arms.
"Contrary to conventional wisdom, with both an inner counter-clockwise pair
and an outer clockwise pair of spiral arms, NGC4622 must have a pair of
leading arms," Byrd said. "With two pairs of arms winding in opposite
directions, one pair must lead and one pair must trail. Which way is which
depends on the disk's rotation. The outer clockwise pair must be the leading
pair if the disk turns clockwise. Alternatively, the inner counter clockwise
pair must be the leading pair if the disk turns counter clockwise."
The team also discovered an outer clockwise single arm, previously hidden by
the stronger outer clockwise arm pair. The galaxy also has a previously
identified inner single counterclockwise arm. This confirms the galaxy must
have a single leading arm. The outer clockwise arm must be the leading arm
if the disk turns clockwise. The inner counter clockwise arm must be the
leading single arm if the disk turns counter clockwise.
The researchers also performed a more complicated analysis of different
color Fourier image components. This revealed the stronger outer clockwise
pair of arms as the leading pair.
Results are also scheduled for January publication in Astronomical Journal.
In 2002, team members first published, to great skepticism, results from a
previous method that indicated the galaxy had a leading pair of spiral arms.
Other astronomers were skeptical of the 2002 announcement, in part, because
the galaxy disk is only tilted about 19 degrees from face-on and because
clumpy dust clouds might be concentrated on one side of the disk, creating
misleading results. In response, the team's new Fourier component method is
actually assisted by the small tilt, and the effects of dust are not used in
the latest analysis.
"Two independent methods now indicate that NGC4622's arms do indeed behave
in a very unusual fashion, with the outer arms winding outward in the same
direction the galaxy turns," said Byrd, a faculty member within UA's College
of Arts and Sciences.
Further studies of the origin of this behavior are needed, the researchers
said. The Hubble Space Telescope image reveals a dark dust lane in the
center which suggests the galaxy may have consumed a smaller companion
galaxy, the researchers said.
This research was supported by NASA and the National Science Foundation.
[NOTE: Images supporting this release are available at
http://uanews.ua.edu/anews2008/jan08/galaxy010808.htm ]
University of Alabama
Tuscaloosa, Alabama
Contact:
Chris Bryant
University of Alabama Assistant Director of Media Relations
205/348-8323
Sources:
Dr. Gene Byrd
Department of physics and astronomy, University of Alabama
205/394-5853
Tarsh Freeman
Department of mathematics, Bevill Community College
800/648-3271, ext. 5167
Dr. Ron Buta
Department of physics and astronomy, University of Alabama
205/348-3792
Dr. Sethanne Howard
Columbia Md.
January 8, 2007
UA Astronomers on Team Describing New Evidence of 'Inconvenient' Galaxy
TUSCALOOSA, Ala. -- Discovery of two new components within a puzzling spiral
galaxy confirm it must have a pair of arms winding in the opposite direction
from most galaxies, according to results being presented today to the
American Astronomical Society meeting in Austin, Texas. Presenting the
results are Drs. Gene Byrd and Ron Buta, from The University of Alabama;
Tarsh Freeman, Bevill Community College; and Dr. Sethanne Howard, retired
from the U.S. Naval Observatory.
"While the existence of a galaxy with a pair of 'backward' arms may seem
like an inconvenient truth to many, our latest analysis indicates it is,
nonetheless, a reality," says Byrd, professor of astronomy at The University
of Alabama.
The galaxy, known as NGC4622, lies 200 million light years away in the
constellation Centaurus.
Spiral arm pairs seen in galaxies are thought to trail, meaning they wind
outward, opposite the direction of rotation of the disk material. Leading
arms, such as the pair reported by the astronomers for NGC4622, do the
opposite, opening outward in the same direction as the rotation of the
galaxy's disk.
Using a Fourier component image method to further analyze a 2001 Hubble
Space Telescope image, the team discovered a previously hidden inner counter
clockwise pair of spiral arms.
"Contrary to conventional wisdom, with both an inner counter-clockwise pair
and an outer clockwise pair of spiral arms, NGC4622 must have a pair of
leading arms," Byrd said. "With two pairs of arms winding in opposite
directions, one pair must lead and one pair must trail. Which way is which
depends on the disk's rotation. The outer clockwise pair must be the leading
pair if the disk turns clockwise. Alternatively, the inner counter clockwise
pair must be the leading pair if the disk turns counter clockwise."
The team also discovered an outer clockwise single arm, previously hidden by
the stronger outer clockwise arm pair. The galaxy also has a previously
identified inner single counterclockwise arm. This confirms the galaxy must
have a single leading arm. The outer clockwise arm must be the leading arm
if the disk turns clockwise. The inner counter clockwise arm must be the
leading single arm if the disk turns counter clockwise.
The researchers also performed a more complicated analysis of different
color Fourier image components. This revealed the stronger outer clockwise
pair of arms as the leading pair.
Results are also scheduled for January publication in Astronomical Journal.
In 2002, team members first published, to great skepticism, results from a
previous method that indicated the galaxy had a leading pair of spiral arms.
Other astronomers were skeptical of the 2002 announcement, in part, because
the galaxy disk is only tilted about 19 degrees from face-on and because
clumpy dust clouds might be concentrated on one side of the disk, creating
misleading results. In response, the team's new Fourier component method is
actually assisted by the small tilt, and the effects of dust are not used in
the latest analysis.
"Two independent methods now indicate that NGC4622's arms do indeed behave
in a very unusual fashion, with the outer arms winding outward in the same
direction the galaxy turns," said Byrd, a faculty member within UA's College
of Arts and Sciences.
Further studies of the origin of this behavior are needed, the researchers
said. The Hubble Space Telescope image reveals a dark dust lane in the
center which suggests the galaxy may have consumed a smaller companion
galaxy, the researchers said.
This research was supported by NASA and the National Science Foundation.
[NOTE: Images supporting this release are available at
http://uanews.ua.edu/anews2008/jan08/galaxy010808.htm ]