Sub-millimetre Astronomy in Full Swing on Southern Skies
http://redorbit.com/news/space/571451/submillimetre_astronomy_in_full_swing_
on_southern_skies/index.html
Impressive set of APEX Results to be published in Special Issue of Astronomy
& Astrophysics
The Atacama Pathfinder Experiment (APEX) 12-m sub-millimetre telescope lives
up to the ambitions of the scientists by providing access to the "Cold
Universe" with unprecedented sensitivity and image quality. As a
demonstration, no less than 26 articles based on early science with APEX are
published this week in the research journal Astronomy & Astrophysics.
Among the many new findings, most in the field of star formation and
astrochemistry, are the discovery of a new interstellar molecule, and the
detection of light emitted at 0.2 mm from CO molecules, as well as light
coming from a charged molecule composed of two forms of Hydrogen.
Using both APEX and the IRAM 30-metre telescope the first astronomical
detection of a charged molecule composed of Carbon and Fluorine - the 'CF+
ion' - was made. Prior to this discovery, only one fluorine-containing
molecular species had been found in space so far, the HF molecule ('hydrogen
fluoride'), consisting of one atom of Hydrogen and one of Fluorine.
The newly discovered molecule, produced through a reaction between Carbon
and the HF molecule, was found in a region adjoining the Orion Nebula, one
of the nearest and most active stellar nurseries in the Milky Way. This
detection provides support to the astronomers' understanding of interstellar
fluorine chemistry, suggesting that hydrogen fluoride is ubiquitous in
interstellar gas clouds.
Another premiere is the detection - also in the Orion star-forming region -
of light emitted by carbon monoxide (CO) at a wavelength of 0.2 mm. These
short wavelengths are very difficult to investigate, both because the water
vapour in the atmosphere attenuates the signal even more severely than
elsewhere in the submillimeter range, but also because they are at the limit
of the telescope's operating range. The detection of CO at these
wavelengths, the very shortest accessible from Earth in any of the
submillimeter 'windows', proves the superb efficiency of APEX.
Light coming from a charged molecule composed of Hydrogen and Deuterium
(H2D+) was detected in several cold clouds in the Southern Sky. The H2D+ ion
is interesting because it traces gas so cold (a few degrees above the
absolute zero!) that only a few molecular species have not frozen out onto
the surfaces of dust grains.
These are not the only significant discoveries made. Other highlights
include the first observations of atomic carbon in the so-called "Pillars of
Creation" in the Eagle Nebula (also known as Messier 16), a sub-millimetre
study of a massive hot core, of a high-mass star forming region, as well as
of a high velocity outflow coming from a young stellar object. Studies of
molecular regions in the dwarf galaxy NGC 6822 and in the starburst galaxy
NGC 253 were also done, proving that APEX can also contribute to the
exploration of extragalactic objects.
Apart from the astronomical studies, a series of contributions deal with the
technical aspects of APEX, such as the telescope itself, its software, its
receivers and spectrometers. The latter were developed at the
Max-Planck-Institut für Radioastronomie in Bonn, Germany and at the Swedish
Chalmers University, while the 0.2 mm receiver was developed at the
University of Cologne (Germany).
APEX at Chajnantor
The APEX telescope, designed to work at sub-millimetre wavelengths, in the
0.2 to 1.5 mm range, passed successfully its Science Verification phase in
July 2005 (see ESO PR 18/05 and ESO PR 25/05), and since then is performing
regular science observations. It is located on the 5100 m high Chajnantor
plateau in the Atacama Desert (Chile), probably the driest place on Earth.
It is a collaborative effort between the Max-Planck-Institut für
Radioastronomie, ESO and the Onsala Space Observatory (Sweden).
With its precise antenna and large collecting area, APEX provides, at this
exceptional location, unprecedented access to a whole new domain in
astronomical observations. Indeed, millimetre and sub-millimetre astronomy
opens exciting new possibilities in the study of the first galaxies to have
formed in the Universe and of the formation processes of stars and planets.
It also allows astronomers to study the chemistry and physical conditions of
molecular clouds, that are dense regions of gas and dust in which new stars
are forming.
APEX is the pathfinder to the ALMA project. In fact, it is a modified ALMA
prototype antenna and is located at the future site of the ALMA observatory.
ALMA will consist of a giant array of 12-m antennas separated by baselines
of up to 14 km and is expected to gradually start operation by the end of
the decade.
The Astronomy & Astrophysics special issue (volume 454 no.2 - August I,
2006) on APEX first results includes 26 articles. They are freely available
in PDF format from the publisher web site.
These results are partly based on APEX science verification data that are
available from the ESO archive at http://www.eso.org/science/apexsv/.
Gregory S. Williams
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