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Session 34 - Real Instruments.
Display session, Tuesday, June 09
Atlas Ballroom,

[34.01] High Resolution Millimeter Wavelength Polarimetry at BIMA

R. Rao, R. M. Crutcher (U. Illinois), R. L. Plambeck, M. C. H. Wright (UC Berkeley)

Polarimetry at far-infrared, sub-millimeter and millimeter wavelengths is a useful probe of the magnetic field structure in regions of star formation. However, most previous polarization observations have been conducted with single dish telescopes (KAO, CSO, JCMT, NRAO 12-meter) with limited angular resolution (greater than 20\arcsec). Polarization observations with interferometer arrays can provide higher angular resolution (about 4\arcsec) images of star-forming regions. We present here the details of a polarimetry system constructed for the Berkeley-Illinois-Maryland Association (BIMA) millimeter array at Hat Creek (California) operating at wavelengths of 3.3 mm (90 GHz) and 1.3 mm (230 GHz). The polarizing element is a quarter wave plate made of Rexolite (cross-linked polystyrene) which has a diectric constant of approximately 2.55. The instrumental response, which is frequency-dependent since the polarizer is chromatic, has been determined to an accuracy of 0.3%. The polarimeter has also been used to monitor a select sample of quasars to determine their time variability. These quasar polarization data complement lower frequency monitoring surveys (less than 15 GHz) and constrain the emission models and magnetic field topology deduced for these objects.

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