Astronomical Research with the Owens Valley Millimeter Array

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AST-9314079. California Institute of Technology. PI: N. Z. Scoville Astronomical Research with the Owens Valley Millimeter Array This award supports research, technological development and student education at the California Institute of Technology's Owens Valley millimeter array. The array is made up of 6 precision 10.4m- diameter antennas, which currently can be positioned out to maximum spacings of 220m north-south and 200m east-west. All the telescopes are equipped with dual-channel (2.6 and 1.3mm) cryogenic SiS receivers. At the shorter wavelength, the highest angular resolution attainable by the array is 1 arcsecond. Approximately 50% of the array's observing time is presently devoted to investigations by non-Caltech astronomers. During the tenure of the past three year grant, the Owens Valley array has obtained aperture synthesis images of molecular emission in domains ranging from the envelopes of evolved stars, to star- forming regions in the Galaxy, as well as the spiral arms and active nuclei of other galaxies; carbon monoxide emission has been detected in high redshift quasars and ultraluminous galaxies at redshifts as high as 3.2. During the last grant period, the observatory also made a number of technical advances, including the construction and placement in service of 3 additional antennas, installation of new beam transport optics, implementation of fully remote receiver tuning capability, construction of a new digital correlator and fiber-optic transmission and delay line system. In the next three year grant period the observatory's scientific programs will include studies of high-redshift galaxies and protogalaxies, infrared-luminous galaxies, the large-scale structure of the Universe, protostars and protoplanetary nebulae, the structure of the Milky Way Galaxy, collimated outflows from young stars, interstellar chemistry and a variety of solar system objects. Planned technical developments in the 1994-1997 period include the intr oduction of sideband separation receivers with integrated first-stage IF amplifiers, doubling the interferometer baseline, introduction of a second continuum channel for each baseline, and the development and testing of low-noise stable radiometers on each telescope to measure and compensate for short- term atmospheric fluctuations in phase which reduce the sensitivity of the array, particularly over large baselines.