The Mopra Millimetre Wave Telescope
Largest in the Southern Hemisphere
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News Release - School of Physics,
University of New South Wales
Tuesday 7th September 1999
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 An
agreement between UNSW and CSIRO has seen the Mopra radio telescope
upgraded to have a solid surface out to its full 22-m diameter.
This now makes it the largest millimetre telescope in the Southern
hemisphere, able to make the most sensitive observations of the
star forming molecular clouds through the heart of our Milky Way
Galaxy.
The first light of the upgraded telescope
will be commemorated at a ceremony on September 24 by Professor
Chris Fell, Deputy Vice-Chancellor of UNSW, and Professor Ron Ekers,
Director of the Australia Telescope National Facility.
The arrival of the new millennium promises
to take millimetre and sub-millimetre astronomy to new heights.
The southern hemisphere is poised for some sharper and sensitive
probing. Interferometers have made sensitive high resolution imaging
possible at these frequencies. The southern hemisphere had been
left out, but the Australia Telescope Compact Array (ATCA) will
soon fill up the gap and become the south's first and the world's
sharpest and most sensitive mm-wave interferometer. It will pave
the way for exciting new scrutiny of the southern sky with the next
generation instrument, the Atacama Large Millimeter Array (ALMA),
to be located in the Chilean Andes.
While fine scrutiny falls in the domain
of interferometers, it is for the single dishes to survey large
regions and identify objects fit for such scrutiny. The southern
sky has also been lacking in mm-wave telescopes. With its recent
size extension, Mopra has become the largest dish in the south.
The only other large southern telescope, the Swedish-ESO sub-millimetre
wave telescope (SEST), better located in the Chilean mountains,
concentrates more on the sub-mm window (wavelengths just less than
1 mm). Thus, the onus of preparing the ground for effective use
of ATCA largely rests with Mopra.
The Mopra Telescope is located at the
foot of Mt Woorut, in the Warrumbungle Moutains of NW NSW. Mt Woorut
is home to Siding Spring Observatory, where Australia's premier
optical telescopes, including the giant 3.9m Anglo
Australian Telescope, are
located.
The size extension of Mopra took place
as a joint venture between UNSW and CSIRO. As a part of this effort,
UNSW will be operating Mopra in mm-waves for the next three years.
Researchers at UNSW will provide observing support to the user community
for six weeks and use another six weeks for some key projects of
their own interest. One project we wish to pursue is the relation
between the structure of a molecular cloud and its star formation
activity. A recent study of two giant molecular clouds of similar
mass, one star-forming and another quiescent, reveals that their
"clump" mass spectra have a similar spectral index, only differing
in their "clump scale sizes". However, in the popular model of a
"turbulence dominated cloud", most of these "clumps" are likely
to be pressure bound and transient structures. Only "gravity bound"
clumps are relevant to star formation and it is necessary to determine
their mass spectra to see if there is any difference between molecular
clouds. Mopra will be engaged in a multi-species mapping of such
clouds to address this question. Identifying protostars of both
low and high mass stars and probing their environment with multi-species
studies is another project we will pursue with Mopra. Studying the
molecular environment of nearby Galaxies, both normal and spiral
is also an area of interest to us.
Maps of three different molecular
lines in the Orion star forming region. Their very different morphologies
illustrates the wealth of information that mm-lines can provide
about an astronomical source. This map was made using the QUARRY
array of the Five College Radio Astronomy Observatory; Ungerechts,
H. et al. 1994, Proceedings of the Zermatt Symposium on Molecular
Clouds.
Size extension is one of the steps in
our effort to make Mopra both sharp and sensitive , capable of carrying
out front-line science projects. Holography has been carried out
to improve the surface accuracy: currently the rms surface error
is better than 0.2 mm. Another holographic run should take us close
to 0.15 mm. This will be 20 times less than the typical observing
wavelength of 3 mm. A new pointing model for the extended antenna
is being developed. An updated User's manual is being prepared to
make observing with Mopra simpler. Our observing support should
make Mopra more user friendly and we also hope to smooth out some
of the rough edges involving data reduction. You can find more about
our millimetre-wave activities on the Mopra
page.
To promote use of Mopra, we held a mini-workshop
on June 17 at UNSW. Following on from this we are organising a three
day workshop at the telescope to provide a hands-on experience with
Mopra. These improvements and support will stimulate the field of
millimetre astronomy amongst Australian scientists, and prepare
us to use the forthcoming millimetre interferometers of the ATCA
and ALMA effectively.
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