The Center for Astrophysical Research in Antarctica (CARA) was formed in 1991 to establish an observatory at the South Pole and to pursue a set of astrophysics research projects which exploit the unique advantages of the high Antarctic site. The projects are knit together by overlapping scientific questions addressable by observations at wavelengths from one micron to one millimeter; by the logistical aspects of running a common observatory at a remote site; and by a common type of experiment which places emphasis on questions approachable with large-scale, uniform, high-sensitivity observations.
At millimeter wavelengths, the evolution of the earliest structures in the universe that eventually formed galaxies and galaxy clusters are studied by measuring the anisotropy in the cosmic microwave background (CMB). The study of molecular clouds, the energetics of star formation, and dynamics of galactic nuclei require observations in the less explored submillimeter windows. Here, spectral lines of neutral carbon (CI) and carbon monoxide (CO) and continuum polarimetry are tools to probe the immediate environment of young stars and the structure, chemistry and magnetic fields of the giant molecular clouds from which stars form. The youngest stars, which condense from the densest parts of the interstellar medium (ISM), are best studied in the near- (2-5 microns) and mid- (10-40 microns) infrared portions of the spectrum. Infrared radiation can penetrate the opaque molecular clouds and provide a direct view of deeply embedded young stars and protostars.
Throughout this large range of wavelengths, from 3 microns to 10 mm, the atmosphere is the major limitation of ground based astronomical observations. The leading cause is the presence and variability of atmospheric water vapor. The South Pole, a high, cold, and dry site, is exceptionally good for this wavelength range because of the low water vapor and high stability of the atmosphere.
Since 1991, the Center has established a year-round observatory at the South Pole; characterized the transparency, darkness, and stability of the Antarctic sky; installed three major telescope facilities and used them to conduct scientific investigations. Among the successes of these investigations are a sensitive detection of CMB anisotropy on degree angular scales and the mapping of large regions of the Galaxy in CI. Now, with facilities in place, with established methods of operating equipment in the Antarctic environment, and with a knowledge of the site characteristics in hand, CARA is realizing the scientific potential from its investments and studying the origins of stars, clouds, and galaxies.
This research is being carried out with an optimized combination of existing telescopes and receivers and with several new instruments constructed by CARA and collaborating U.S. and international scientists. Among the existing facilities is Antarctic Submillimeter Telescope and Remote Observatory (AST/RO), a 1.7 m submillimeter-wave telescope surveying the 609 micron [CI] emission from the Galactic plane, star formation regions, high-latitude translucent clouds, the Magellanic Clouds, and nearby galaxies. New AST/RO array receivers will permit rapid mapping in the 370 micron line of CI and in the submillimeter lines of CO and other species.
The 0.6 m South Pole Infrared Explorer (SPIREX) infrared telescope has been revitalized with a state-of-the-art InSb array called Abu, a collaborative project among CARA, U.S., and Australian collaborators. The SPIREX/Abu combination enables wide-field, deep surveys of star formation in our Galaxy and in the Magellanic Clouds at wavelengths between 2 and 5 microns. The investigation of the Cosmic Microwave Background (CMB) anisotropy is a major thrust of CARA. Recently the analysis of the last year of the Python CMB observations were published, and this coming season the Degree Angular Scale Interferometer (DASI), an interferometric telescope, will be deployed to complement the Viper CMB telescope. Together these instruments will characterize the anisotropy in the CMB at angular scales down to 0.1 degree allowing unprecedented limits to be placed on models of early structure growth in the universe. In November 2000, Viper will be outfitted with a sensitive multifrequency bolometer array (ACBAR) to increase further the frequency and angular range covered by the CARA CMB instruments.
During this past year, there have been many new accomplishments. The final analysis of the last year of Python CMB data are now published with exciting, competitive results at larger angular scales. The Viper telescope has continued its characterization of the CMB anisotropy and has detected the Sunyaev-Zel'dovich effect toward nearby galaxy clusters. AST/RO and SPIREX/Abu have made successful transitions to user-facility instruments with proposals solicited from the astronomical community at large. The construction of DASI was completed on schedule and it is now in transit to the Pole. The Submillimeter Polarimeter Antarctic Remote Observing (SPARO) polarimetric bolometer array was tested succesfully on the Viper telescope and will be obtaining large scale polarimetric submillimeter maps of dust emission from the Galactic center this Fall. The predeployment test mounting of the South Pole Imaging Fabry-Perot Interferometer (SPIFI) on the AST/RO telescope and the commissioning tests of SPIFI on the James Clark Maxwell Telescope (JCMT) on Mauna Kea were successful ensuring a smooth deployment of SPIFI in November 2000. SPIFI will permit the large-scale imaging of emission line regions over a broad wavelength range in the submillimeter. Characterization of the site continues, increasing the time baseline for many indicators and adding new indicators, such as a full year of monitoring the mid-infrared sky brightness.
The CARA program of outreach continues to grow, even as the end of CARA begins to loom on the horizon. Planning has begun for the programs that will encompass and succeed those established by CARA and strategic collaborations have been established that will ensure the partnerships and practices developed by CARA will not languish. Precollege education, via the Space Explorers Program, remains the primary focus of the CARA program. In addition, over the past year CARA post-secondary programs have grown with the blossoming of the Advanced Technological Education program, the hosting of enrichment workshops for K-12 and college educators and more active management of undergraduate research experiences.
Planning for the post CARA era has become a focus of CARA. Through discussions with all CARA participants, with key members of AMANDA, and with other successful science organizations, a concrete plan for the establishment of an enduring scientifically managed organization for conducting scientific research at the South Pole has emerged. The launching of this organization is the major goal for the CARA directorship during the next year.