Cambridge, MA — With four out of the eight antennas now operational,
the collection of images from the world’s first sub millimeter array
(SMA) has begun. Exploring one of astronomy’s last frontiers at a
site near the summit of Mauna Kea in Hawaii, the SMA offers a unique
opportunity to observe objects in unprecedented detail. Acting as an
interferometer similar to the Very Large Array in New Mexico, the SMA
will ultimately combine the electronic signals from eight 6-meter
antennas to imitate the resolving power of a much larger telescope.
When placed at their widest separation, the SMA’s eight antennas will
act like a single giant telescope more than 1,600 feet in diameter,
equivalent to the length of five football fields.

"An imaging array at submillimeter wavelengths has applications in many
exciting areas of astrophysics", says James Moran, SMA Director at the
Harvard-Smithsonian Center for Astrophysics. "The SMA will allow us to
peer into regions that are obscured at optical and infrared wavelengths
to study low-energy emissions from cold dust and molecules. These
emissions often arise in star-forming regions, protoplanetary disks,
active regions of distant galaxies, and solar system bodies — all the
places where discerning more detail using the high-resolution of the
SMA will be invaluable."

The SMA project is a collaboration between the Smithsonian Astrophysical
Observatory (SAO) in Cambridge, MA, and the Academia Sinica Institute
of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan. "The
collaboration on the SMA has been very beneficial for both our
organizations", says K.Y. Lo, Director of ASIAA. "The addition of
the two telescopes by ASIAA to the six built by SAO will double the
observing speed of the SMA. ASIAA has also been able to build up rapidly
to an international level, both scientifically and technically, through
the involvement in the construction of this unique facility."

High-resolution observations at submillimeter wavelengths are very
difficult from the ground because of the partial transparency and
turbulence of the atmosphere. The high altitude of the site mitigates
the transparency problem and special techniques add the equivalent of
adaptive optics.

The SMA is a natural next step following the highly successful millimeter
wave arrays operating at longer wavelengths. It has been under
construction in Hawaii since 1995 and is expected to be fully operational
by mid 2003.

In its current configuration, the Array utilizes 4 antennas at
wavelengths of 1.3 and 0.9 mm with a restricted bandwidth of 320 MHz.
In its final configuration the Array will have a bandwidth of 2000 MHz.
In addition, the nearby radio facilities of the Caltech Submillimeter
Observatory (CSO) and the James Clerk Maxwell Telescope (JCMT) will
be connected to the SMA to form a 10-antenna array for special
observations.

Initial observations made in the Fall of 2001 resulted in the first
interferometric images ever made at a radio wavelength shorter than
1.3 mm. "These results clearly demonstrate the range of applications
and great potential of the instrument as it approaches completion. We
are about to explore one of the last windows to the Universe," says
Paul Ho, SMA Project Scientist at the Center for Astrophysics.

The first submillimeter wavelength images obtained were of the molecular
outflow of carbon monoxide in the Egg Nebula (AFGL 2688), a proto-
planetary nebula. The image revealed two bipolar outflows that were
previously documented from longer wavelength observations.

When an image of Mars was taken, profiles of carbon monoxide were
measured across the planetary disk clearly revealing the difference in
temperatures between the planet’s surface and atmosphere. A vertical
profile of the atmospheric temperature was also obtained. Further
development of these capabilities will lead to a better understanding
of weather patterns on Mars and other planets and their satellites.

Nineteen observations, spaced over a year, were made of the luminosity
of the radio source surrounding the black hole in the center of the
Galaxy known as Sagittarius A*. The results clearly show that the source
is highly variable. This type of measurement will help establish the
nature of the accretion disk and possible jet associated with this
black hole and others.

In its final configuration the Array will be able to study the most
distant objects in the universe. For example the most distant quasar
known, J104433.04-012502.2 at a redshift of 5.8 has been detected by
the JCMT at a level of 10 mJy, but no information about its structure
or radio spectral lines has been determined.

With its high spectral and angular resolution the SMA will be able to
trace astronomical gas flows in great detail and is expected to provide
important insight into the mechanism by which molecular clouds collapse
into stars and planets.

Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian
Center for Astrophysics (CfA) is a collaboration between the
Smithsonian Astrophysical Observatory and the Harvard College
Observatory. CfA scientists, organized into seven research divisions,
study the origin, evolution, and ultimate fate of the Universe.

ASIAA is headquartered in Taipei, Taiwan. The Institute of Astronomy
and Astrophysics is part of the Academia Sinica.

For more information on the SMA program, visit our website at
http://sma-www.harvard.edu/