Trade.Information

Research persons: Carlos De Breuck,Ernst Kreysa,Giorgio Siringo

Location: Max-Planck-Institut für Radioastronomy,Auf dem Hügel 69,D-53121 Bonn, Germany

Details

The world's largest bolometer camera for submillimetre astronomy is now in
service at the 12-m APEX telescope, located on the 5100m high Chajnantor plateau
in the Chilean Andes. LABOCA was specifically designed for the study of
extremely cold astronomical objects and, with its large field of view and very
high sensitivity, will open new vistas in our knowledge of how stars form and
how the first galaxies emerged from the Big Bang
A large fraction of all the gas in the Universe has extremely cold temperatures
of around minus 250 degrees Celsius, a mere 20 degrees above absolute zero,"
says Karl Menten, director at the Max Planck Institute for Radioastronomy (MPIfR)
in Bonn, Germany, that built LABOCA. "Studying these cold clouds requires
looking at the light they radiate in the submillimetre range, with very
sophisticated detectors."
Astronomers use
bolometers
for this task, which are, in essence, thermometers. They detect incoming
radiation by registering the resulting rise in temperature. More specifically, a
bolometer detector consists of an extremely thin foil that absorbs the incoming
light. Any change of the radiation's intensity results in a slight change in
temperature of the foil, which can then be registered by sensitive electronic
thermometers. To be able to measure such minute temperature fluctuations
requires the bolometers to be cooled down to less than 0.3 degrees above
absolute zero, that is below minus 272.85 degrees Celsius.
"Cooling to such low temperatures requires using liquid helium, which is no
simple feat for an observatory located at 5100m altitude," says Carlos De Breuck,
the APEX instrument scientist at ESO.
Nor is it simple to measure the weak temperature radiation of astronomical
objects. Millimetre and submillimetre radiation opens a window into the
enigmatic cold Universe, but the signals from space are heavily absorbed by
water vapour in the Earth's atmosphere. "It is a bit as if you were trying to
see stars during
This is why telescopes for this kind of astronomy must be built on high, dry
sites, and why the 5100m high plateau at Chajnantor in the extremely dry Atacama
Desert was chosen. Even under such optimal conditions the heat from Earth's
atmosphere is still a hundred thousand times more intense than the tiny
astronomical signals from distant galaxies. Very special software is required to
filter such weak signals from the overwhelming disturbances.
LABOCA (LArge BOlometer Camera) and its associated software were developed by
MPIfR. "Since so far there are no commercial applications for such instruments
we have to develop them ourselves," explains Ernst Kreysa, from MPIfR and head
of the group that built the new instrument.
A bolometer camera combines many tiny bolometer units into a matrix, much like
the pixels are combined in a digital camera. LABOCA observes at the
submillimetric wavelength of 0.87 mm, and consists of 295 channels, which are
arranged in 9 concentric hexagons around a central channel. The angular
resolution is 18.6 arcsec, and the total field of view is 11.4 arcmin, a
remarkable size for instruments of this kind.
"The first astronomical observations with LABOCA have revealed its great
potential. In particular, the large number of LABOCA's detectors is an enormous
improvement over earlier instruments," says Giorgio Siringo from MPIfR and
member of the LABOCA team. "LABOCA is the first camera that will allow us to map
large areas on the sky with high sensitivity."
The Atacama Pathfinder Experiment (APEX) where LABOCA is installed is a
new-technology 12-m telescope, based on an ALMA prototype antenna, and operating
at the ALMA site. It has modified optics and an improved antenna surface
accuracy, and is designed to take advantage of the excellent sky transparency
working with wavelengths in the 0.2 to 1.4 mm range.
"APEX is located a mere 2 km from the centre of the future ALMA array. The new
LABOCA camera will be very complementary to ALMA, as its very wide view will
find thousands of galaxies which will be observed in great detail with ALMA,"
says De Breuck.
About The Researchers:
Carlos De Breuck,
Place de Mogador, 91300 Massy, France
Work Address:
Institut d’Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
Email:
debreuck@iap.fr
Telephone:
+33-1-44328124 (work), +33-1-44328124 (fax work), +33-1-69206071 (home)
ESO fellow at Garching
Office: 411
Phone: +49-89-3200-6613
 
Ernst Kreysa
Max-Planck-Institut für Radioastronomie
Auf dem Hügel 69
D-53121 Bonn
Tel: +49 228 525 269
Fax: +49 228 525 229
Room: 1.57
Email: ekreysa@mpifr-bonn.mpg.de
 
Giorgio Siringo
Postdoctoral Research Fellow in the
Millimeter and Submillimeter Astronomy Group
Max-Planck-Institut für Radioastronomie
Auf dem Hügel 69
D-53121 Bonn
Office: Room 1.58
Tel: +49 228 525 270
Fax: +49 228 525 229
 
Karl M. Menten
Director for
Millimeter and Submillimeter Astronomy
at the
Max-Planck-Institut für Radioastronomy
Auf dem Hügel 69
D-53121 Bonn
Office: Room 2.47
Tel: +49 228 525 297
Fax: +49 228 525 435
Funded:
APEX is a collaboration between
the Max Planck Institute for
Radioastronomy, Onsala Space
Observatory and ESO.
In The Images-
1.Carlos De Breuck,
2.The LABOCA Camera installed on the APEX telescope at the 5100m high
Chajnantor site in Chile. LABOCA is a 'thermometer camera' with 295 detectors
and a field of view of 11.4 arcmin
3.Comparison between an image of the Galactic HII region RCW 120 in the
visible (R-band; as obtained by the ESO Schmidt Telescope) and in the
submillimetre with LABOCA on APEX, highlighting the need to observe in this
wavelength range. The LABOCA image has an exposure of only slightly more than 3
hours. The expanding shell causes the surrounding gas to collapse into clumps,
which are the cradles of massive stars. As the gas in these clumps is still very
cold, around -250 degrees Celsius, they can only be seen at submillimetre
wavelengths. Thanks to the high sensitivity and large field of view of LABOCA,
astronomers could detect clumps that are four times fainter than was possible
before. As the brightness is also a measure of the mass of these stellar
embryos, this will allow scientists to study the formation of more
representative, less massive stars