February 19, 2001
UCSC makes a strong showing at the AAAS meeting in San Francisco
Astronomers, physicists lead way at annual session
By Tim Stephens
Eleven researchers from the University of California, Santa Cruz, gave presentations
at the annual meeting of the American Association for the Advancement of Science
(AAAS) in San Francisco, February 15-20. Leading the pack were a half-dozen UCSC
astronomers, speaking on topics ranging from adaptive optics to galaxy formation.
In addition, Chancellor M.R.C. Greenwood gave a keynote address at a session on "Cultivating
the Civic Scientist." In her talk, "Civic Scientist, Civic Duty,"
Greenwood urged scientists to recognize the public's interest in and support of science
and to become involved in their local communities through activities such as serving
on textbook selection committees.
The following summaries highlight some of the presentations by UCSC scientists in
the areas of astronomy, cosmology, and physics.
Astronomy and Adaptive Optics
Jerry Nelson, professor of astronomy and astrophysics and director of the Center
for Adaptive Optics, discussed the latest developments in the field of adaptive optics
in one of the meeting's Topical Lectures. Adaptive optics is used in astronomy to
correct for the blurring effect of turbulence in Earth's atmosphere. Using sophisticated
technology to actively compensate for changing distortions that cause blurring of
images, adaptive optics promises to revolutionize ground-based astronomy. It will
be a critical component of the next generation of large telescopes, such as the planned
30-meter California Extremely Large Telescope (CELT). Nelson and other UC astronomers
are currently working on the conceptual design for CELT. The
Center for Adaptive Optics, headquartered at UCSC and funded by the National
Science Foundation, is the national leader in the advancement and application of
adaptive optics technology.
FROM GAS AND GRAVITY TO GALAXIES: A COSMIC COUNTDOWN
One of the great challenges of cosmology is to explain how galaxies formed and
evolved. Astronomers study galaxies near and far for clues to this "cosmic conundrum."
This AAAS session brought together some of the leading researchers in the field,
including three from UC Santa Cruz, to present their latest findings.
Puragra (Raja) Guhathakurta: "The Andromeda Spiral Galaxy and its Dwarf
Satellites: A Fossil Record of Galaxy Formation and Evolution"
The galaxy-formation process has left behind telltale clues that lie subtly hidden
within the properties of galaxies, some of which are near enough to allow detailed
studies of individual stars within them. Guhathakurta, associate professor of astronomy
and astrophysics, has been studying the nearby Andromeda spiral galaxy (M31) and
its dwarf satellite galaxies. His findings support the idea that the stellar halos
of large galaxies like Andromeda formed through an accretion process involving mergers
of smaller satellites. The evidence comes from a survey of the chemical compositions
of stars in Andromeda's halo. In addition, Guhathakurta has found evidence that the
two dwarf galaxies closest to Andromeda (M32 and NGC205) are being tidally disrupted
by the larger galaxy's gravitational pull and will eventually merge with it.
David Koo: "Weighing Galaxies Billions of Light Years Away: A New Approach"
While Guhathakurta studies our nearest galactic neighbors, David Koo observes galaxies
billions of light-years away, in effect traveling back in time to view the earliest
stages of galaxy formation. Koo, a professor of astronomy and astrophysics, and his
colleagues have made important advances by combining Hubble Space Telescope (HST)
images with spectroscopic studies using the Keck Telescopes. Free of atmospheric
blurring, HST's sharp images provide information on a galaxy's size (or radius),
while spectra gathered with the 10-meter Kecks yield information on internal velocity
or rotation speed. Together, these measurements enable the researchers to determine
the masses of extremely distant galaxies. Mass measurements provide an essential
link to theoretical models of galaxy formation and evolution. Interestingly, Koo
has observed some very bright galaxies with relatively low masses. He discussed the
implications of these findings for theories of how galaxies are put together.
Garth Illingworth: "Elliptical Galaxies: Oldest, Cleanest, Biggest"
Illingworth, a professor of astronomy and astrophysics, studies galaxies that occur
in dense clusters of hundreds or thousands of galaxies. Most of the galaxies in these
clusters are elliptical galaxies, whereas most galaxies outside of clusters are spirals,
like the Milky Way and Andromeda galaxies. Like Koo, Illingworth studies the motion
of gas and stars within galaxies and uses that information to determine their masses.
Koo, Illingworth, Guhathakurta, and UCSC astronomer Sandra Faber are leaders of a
project called DEEP (Deep Extragalactic Evolutionary Probe), which aims to gather
detailed observations of around 50,000 faint galaxies in the next several years with
a powerful new spectrograph on the Keck II Telescope.
REBUILDING THE GALACTIC NEIGHBORHOOD: GALAXY COLLISIONS IN LOCAL GROUPS
Douglas N. C. Lin: "Once and Future Local Group: The Role of Collisions
(Theory)"
Lin, a professor of astronomy and astrophysics, will discuss the history of the Local
Group of galaxies, which includes the Milky Way, Andromeda, and their dwarf satellites.
Astronomers have good evidence that galaxies in the Local Group have collided and
merged in the past, and that galaxy mergers are still taking place. But they can
observe only snapshots of the process, because it takes hundreds of millions of years
to complete. Mathematical models of the physics involved in galaxy collisions can
help astronomers interpret their observations. Lin will describe how the gravitational
tug of a large galaxy can cause tidal disruption of a dwarf satellite and eventually
cause it to merge with the larger galaxy.
MATTER AND ANTIMATTER: NOT QUITE A MIRROR IMAGE
Michael Dine: "Why the Universe is Made of Matter"
The seemingly unremarkable fact that the universe is full of matter turns out to
be something physicists can't quite account for. According to the big bang theory,
equal amounts of matter and antimatter were created at the birth of the universe.
Somehow, within a fraction of a nanosecond after the big bang, matter gained the
upper hand. Two new accelerators have begun to yield results that could reveal exactly
how the symmetry between matter and antimatter is broken. The challenge for theorists
is to incorporate the new experimental results into a theoretical framework that
satisfactorily accounts for the observed asymmetry. Dine, professor of physics and
a leading theorist, discussed various ideas put forth to explain the source of the
asymmetry that enabled matter to dominate the universe. (See
longer story.)
