Andrew Yee[_1_]
March 7th 07, 05:48 AM
W. M. Keck Observatory
Media Contact:
Laura K. Kino****a
W. M. Keck Observatory
65-1120 Mamalahoa Hwy.
Kamuela, HI 96743
(808) 885-7887
March 6th, 2007
Fundamental Property of Galaxies Discovered at W. M. Keck Observatory
Kamuela -- A new study using data collected by the W. M. Keck Observatory in
Hawaii has revealed that certain fundamental properties of galaxies have
actually changed very little over the last 8 billion years, nearly half of
the age of the universe.
According to the research, the relationship between a galaxy's mass and a
new speed indicator that measures movement of its stars and gas remains the
same for all forms of galaxies, from spirals like our own Milky Way, to
elliptical galaxies, and even the so-called "train wrecks" left over by
galactic mergers.
"Surprisingly, if you use this new speed indicator to measure the motions of
stars and gas in a galaxy, you can predict the mass in stars the galaxy has
with pretty high accuracy," said Susan Kassin, a post-doctoral researcher at
the University of California, Santa Cruz and lead author of the study.
Galaxies like our Milky Way are made up of billions of stars formed into a
spiral disk along with some gas. Like a spinning pinwheel, our galaxy also
spins, but at a speed of a few hundred kilometers per second.
It's known that half of the age of the universe ago, many galaxies look more
disheveled, as they are assembled through galaxy collisions and accretion of
new gas and stars. According to the research, disheveled galaxies and the
remnants of galaxy collisions have mixed-up velocities in addition to some
orderly rotation. Furthermore, the research found that when all these
velocities are totaled up, the total amount of motion was found to be
similar to that of more well behaved galaxies. "This suggests that the
mixed-up velocities may settle down to orderly rotation over time as the
universe ages," said Ben Weiner, a researcher at Steward Observatory at the
University of Arizona and a co-author of the study.
There are three main types of galaxies in the universe: spiral or disk-like
galaxies like our own Milky Way, elliptical or cloud-like galaxies, and the
remnants of galaxy collisions. It was previously known that when it comes to
spiral galaxies, the more massive the galaxy, the faster its stars and gas
rotate. The relation between the mass in stars of spiral galaxies and the
rotation speed of their stars and gas is known as the Tully-Fisher relation.
When it comes to elliptical galaxies, the more massive a galaxy is, the
faster the random motions of its stars. This relation is known as the
Faber-Jackson relation. The latest research went a step further; discovering
a new relation between how massive a galaxy is and a new speed indicator
that takes into account both rotation velocity and random or disordered
motion. This new relation applies to spiral, elliptical, and other types of
galaxies, like disheveled galaxies or the remnants of galaxy collisions, and
has remained essentially the same over the past 8 billion years -- roughly
half the age of the universe.
Kassin, Weiner, and the other researchers were able to bring together both
the Tully-Fisher and Faber-Jackson relations -- and include "disturbed" or
train-wreck galaxies which previously didn't figure in either -- by using a
new speed indicator, a number which when applied to galaxies, allows
astronomers to better mathematically define the movement of stars.
"This relation holds for all the galaxies, no matter what they look like,"
Kassin said. "It ties together the Faber-Jackson relation with the
Tully-Fisher relation and works for all kinds of odd-ball galaxies that are
more common in the early universe."
According to Sandra Faber, co-author of the study and one of the namesakes
of the Faber-Jackson relation which she helped develop in 1976, the research
is believed to reflect a fundamental property of the universe.
"Both of these relations were imprinted by the nature of fluctuations that
made galaxies in the first place," she said.
The recent study involved 544 distant galaxies of various types, which
according to Kassin makes this the largest study to date of the speed and
movement of distant galaxies' stars and other matter. The galaxies studied
ranged in redshift from 0.1 to 1.2, which means their light was emitted
between 2 billion and 8 billion years ago. Redshift is a way of gauging the
distance of an object by measuring how much of the wavelength of its light
has shifted toward the redder regions of the spectrum due to galaxies moving
away from us because of the expansion of the universe. It is similar to the
Doppler Effect which involves changes in sound from an object moving away
from oneself.
Kassin said the DEIMOS spectrograph at Keck II, one of two 10-meter
telescopes the observatory operates on the summit of Mauna Kea, was key to
obtaining the amount of data necessary for the study. "Without it, we
wouldn't have been able to have anything close to this large of a sample,"
she said. Additional data came from the Hubble Space Telescope and the
Canada-France-Hawaii Telescope, which is also located atop Mauna Kea. The
results of the research have been presented in a study to be published in a
special issue of "Astrophysical Journal Letters" devoted to the initial
results of a far-reaching study of galaxies know as AEGIS, for
All-wavelength Extended Groth Strip International Survey. AEGIS involves
nearly 100 scientists from 16 institutions in Europe, North America, and
Asia studying a certain area of the sky using a variety of wavelengths
ranging from X-rays to radio and including ultraviolet and visible light.
For more information see the Web site at
http://aegis.ucolick.org
Funding for this research was provided by the National Science Foundation
and NASA. The study was also co-authored by David Koo, Justin Harker, Anne
Metevier, Andrew Phillips, Jg Diemand, Nicholas Konidaris, Kai Noeske and of
UCSC; Jennifer Lotz of the National Optical Astronomical Observatories;
Kevin Bundy of the University of Toronto; Michael Cooper and Darren Croton
of the University of California at Berkeley and Christopher Willmer of
Steward Observatory at the University of Arizona.
The W. M. Keck Observatory is operated by the California Association for
Research in Astronomy (CARA), a non-profit 501 (c) (3) corporation whose
governing board consists of directors from the California Institute of
Technology and the University of California. In addition, the National
Aeronautics and Space Administration and the W. M. Keck Foundation each have
liaisons to the board. Construction of the twin Keck telescopes and domes
was made possible with generous grants totaling more than $140 million from
the W. M. Keck Foundation in Los Angeles.
Media Contact:
Laura K. Kino****a
W. M. Keck Observatory
65-1120 Mamalahoa Hwy.
Kamuela, HI 96743
(808) 885-7887
March 6th, 2007
Fundamental Property of Galaxies Discovered at W. M. Keck Observatory
Kamuela -- A new study using data collected by the W. M. Keck Observatory in
Hawaii has revealed that certain fundamental properties of galaxies have
actually changed very little over the last 8 billion years, nearly half of
the age of the universe.
According to the research, the relationship between a galaxy's mass and a
new speed indicator that measures movement of its stars and gas remains the
same for all forms of galaxies, from spirals like our own Milky Way, to
elliptical galaxies, and even the so-called "train wrecks" left over by
galactic mergers.
"Surprisingly, if you use this new speed indicator to measure the motions of
stars and gas in a galaxy, you can predict the mass in stars the galaxy has
with pretty high accuracy," said Susan Kassin, a post-doctoral researcher at
the University of California, Santa Cruz and lead author of the study.
Galaxies like our Milky Way are made up of billions of stars formed into a
spiral disk along with some gas. Like a spinning pinwheel, our galaxy also
spins, but at a speed of a few hundred kilometers per second.
It's known that half of the age of the universe ago, many galaxies look more
disheveled, as they are assembled through galaxy collisions and accretion of
new gas and stars. According to the research, disheveled galaxies and the
remnants of galaxy collisions have mixed-up velocities in addition to some
orderly rotation. Furthermore, the research found that when all these
velocities are totaled up, the total amount of motion was found to be
similar to that of more well behaved galaxies. "This suggests that the
mixed-up velocities may settle down to orderly rotation over time as the
universe ages," said Ben Weiner, a researcher at Steward Observatory at the
University of Arizona and a co-author of the study.
There are three main types of galaxies in the universe: spiral or disk-like
galaxies like our own Milky Way, elliptical or cloud-like galaxies, and the
remnants of galaxy collisions. It was previously known that when it comes to
spiral galaxies, the more massive the galaxy, the faster its stars and gas
rotate. The relation between the mass in stars of spiral galaxies and the
rotation speed of their stars and gas is known as the Tully-Fisher relation.
When it comes to elliptical galaxies, the more massive a galaxy is, the
faster the random motions of its stars. This relation is known as the
Faber-Jackson relation. The latest research went a step further; discovering
a new relation between how massive a galaxy is and a new speed indicator
that takes into account both rotation velocity and random or disordered
motion. This new relation applies to spiral, elliptical, and other types of
galaxies, like disheveled galaxies or the remnants of galaxy collisions, and
has remained essentially the same over the past 8 billion years -- roughly
half the age of the universe.
Kassin, Weiner, and the other researchers were able to bring together both
the Tully-Fisher and Faber-Jackson relations -- and include "disturbed" or
train-wreck galaxies which previously didn't figure in either -- by using a
new speed indicator, a number which when applied to galaxies, allows
astronomers to better mathematically define the movement of stars.
"This relation holds for all the galaxies, no matter what they look like,"
Kassin said. "It ties together the Faber-Jackson relation with the
Tully-Fisher relation and works for all kinds of odd-ball galaxies that are
more common in the early universe."
According to Sandra Faber, co-author of the study and one of the namesakes
of the Faber-Jackson relation which she helped develop in 1976, the research
is believed to reflect a fundamental property of the universe.
"Both of these relations were imprinted by the nature of fluctuations that
made galaxies in the first place," she said.
The recent study involved 544 distant galaxies of various types, which
according to Kassin makes this the largest study to date of the speed and
movement of distant galaxies' stars and other matter. The galaxies studied
ranged in redshift from 0.1 to 1.2, which means their light was emitted
between 2 billion and 8 billion years ago. Redshift is a way of gauging the
distance of an object by measuring how much of the wavelength of its light
has shifted toward the redder regions of the spectrum due to galaxies moving
away from us because of the expansion of the universe. It is similar to the
Doppler Effect which involves changes in sound from an object moving away
from oneself.
Kassin said the DEIMOS spectrograph at Keck II, one of two 10-meter
telescopes the observatory operates on the summit of Mauna Kea, was key to
obtaining the amount of data necessary for the study. "Without it, we
wouldn't have been able to have anything close to this large of a sample,"
she said. Additional data came from the Hubble Space Telescope and the
Canada-France-Hawaii Telescope, which is also located atop Mauna Kea. The
results of the research have been presented in a study to be published in a
special issue of "Astrophysical Journal Letters" devoted to the initial
results of a far-reaching study of galaxies know as AEGIS, for
All-wavelength Extended Groth Strip International Survey. AEGIS involves
nearly 100 scientists from 16 institutions in Europe, North America, and
Asia studying a certain area of the sky using a variety of wavelengths
ranging from X-rays to radio and including ultraviolet and visible light.
For more information see the Web site at
http://aegis.ucolick.org
Funding for this research was provided by the National Science Foundation
and NASA. The study was also co-authored by David Koo, Justin Harker, Anne
Metevier, Andrew Phillips, Jg Diemand, Nicholas Konidaris, Kai Noeske and of
UCSC; Jennifer Lotz of the National Optical Astronomical Observatories;
Kevin Bundy of the University of Toronto; Michael Cooper and Darren Croton
of the University of California at Berkeley and Christopher Willmer of
Steward Observatory at the University of Arizona.
The W. M. Keck Observatory is operated by the California Association for
Research in Astronomy (CARA), a non-profit 501 (c) (3) corporation whose
governing board consists of directors from the California Institute of
Technology and the University of California. In addition, the National
Aeronautics and Space Administration and the W. M. Keck Foundation each have
liaisons to the board. Construction of the twin Keck telescopes and domes
was made possible with generous grants totaling more than $140 million from
the W. M. Keck Foundation in Los Angeles.