Research Objectives:
Astronomy is undergoing a revolutionary transformation, where for the first time researchers can observe the full range of electromagnetic radiation emitted by astronomical sources. One of the newly developed and least explored bands is the submillimeter, at frequencies from about 300 giga-Hertz up into the tera-Hertz range. Submillimeter-wave radiation is emitted by dense gas and dust between the stars, and submillimeter-wave observations allow scientists to study in unprecedented detail the galactic forces acting on that gas and the star formation processes within it.
The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is a 1.7-meter, single-dish instrument that has been operating since 1995 in several submillimeter bands. It has made position-position-velocity maps of submillimeter-wave spectral lines with arcminute resolution over regions of sky that are several square degrees in size. AST/RO is a valuable complement to the planned arrays, which are inefficient when observing large areas because of their small field of view. AST/RO can observe molecular clouds throughout the fourth quadrant of the Milky Way and the Magellanic Clouds to locate star-forming cores and study in detail the dynamics of dense gas in our own galaxy. AST/RO studies are showing how molecular clouds are structured, how the newly formed stars react back on the cloud, and how galactic forces affect cloud structure. They have also shown that the structure of molecular clouds is affected by their heavy element content and by their proximity to spiral arms.
The project has produced extensive high sensitivity maps of several atomic and molecular transitions toward the Galactic Center and an unbiased survey of molecular and atomic gas in the fourth quadrant of the Galaxy. The telescope operates continuously through the Austral winter. Observations at terahertz frequencies are available with the TREND receiver, a 1.4 THz hot electron bolometer detector system, and with SPIFI, the South Pole Imaging Fabry-Perot Interferometer.
Essential to AST/RO’s capabilities is its location at Amundsen–Scott South Pole Station. Most submillimeter radiation is absorbed by irregular concentrations of atmospheric water vapor before it reaches the earth’s surface. The dry air over South Pole Station allows an accurate intercomparison of submillimeter-wave power levels from locations on the sky separated by several degrees. This is essential to the study of submillimeter-wave radiation on the scale of the Milky Way and its companion galaxies.
Project researchers will use recently installed receivers in the Terahertz frequency band (SPIFI, TREND) to map highly-excited lines of carbon monoxide and other molecules toward star-forming regions in the Milky Way and nearby galaxies and to map emission from ionized nitrogen the second strongest line emitted from the interstellar medium) toward the Galactic Center. They will begin a survey of atomic and molecular lines from the Lupus and Chameleon clouds which are being intensively studied at infrared wavelengths with the Spitzer Space Telescope. The data will be made freely available.
