Millimeter and Submillimeter Interferometry of Astronomical Sources

Abstract

The development of millimeter and submillimeter interferometers was
\nbasically motivated by the discovery, in the late 1960s and early 1970s,
\nthat trace amounts of molecular gas in the interstellar medium could be
\ndetected through millimeter-wave spectral line emission (cf Rank et al
\n1971). The observed lines reflected the presence of unexpectedly large
\namounts of molecular hydrogen, H_2 organized into giant molecular clouds
\nwhere star formation takes place in the Milky Way and in other galaxies
\n(e.g. Sanders et aI 1984). A wide variety of millimeter-wave molecular lines
\nhave also been identified in the circumstellar shells around evolved stars
\n(cf Loup et al 1993). The intensities and Doppler shifts of these mm-wave
\nspectral lines provide information about the density, temperature,
\nkinematics, and chemical state of the gas. In addition, interstellar and
\ncircumstellar dust can be studied through observations of millimeter-wave continuum radiation. The success of centimeter-wavelength interferometers
\nsuch as the VLA in producing fundamental new science argued
\nthat millimeter-wavelength astronomy would also benefit from the high
\nangular resolution provided by interferometers.