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Proceedings Paper

Versatile IF polarimeter at the IRAM 30m telescope
Author(s): Clemens Thum; Helmut Wiesemeyer; David Morris; Santiago Navarro; Marc Torres
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Paper Abstract

We report on the commissioning of a polarimeter operating at the intermediate frequency (150 MHz) of the IRAM 30m telescope. The polarimeter adds, with suitable phase shifts, the amplitudes of two orthogonally linearly polarized heterodyne receivers, and determines from these signals all four Stokes parameters. The polarimeter allows continuum as well as spectral line observations in all millimeter atmospheric windows accessible with the 30m telescope. The instrumental phase between the two receivers, controlled through a phase shifter, does not exceed one degree (rms) at 3mm. Instrumental polarization on boresight is found to be small, below one percent for Stokes U and V. Limitations due to beam polarization are discussed. We present results from the first large scale 3mm polarization survey started in 1999. About 100 Active Galactic Nuclei with flux densities stronger than approximately 0.8 Jy were observed, many of them repeatedly. Linear polarization larger than 10 percent is found in several sources at several epochs. We briefly describe results from two spectro--polarimetric surveys: SiO maser stars and methanol masers. Polarization is easily detected in both groups.

Paper Details

Date Published: 14 February 2003
PDF: 12 pages
Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003);
Show Author Affiliations
Clemens Thum, IRAM (France)
Helmut Wiesemeyer, IRAM (France)
David Morris, IRAM (France)
Santiago Navarro, IRAM (Spain)
Marc Torres, IRAM (France)

Published in SPIE Proceedings Vol. 4843:
Polarimetry in Astronomy
Silvano Fineschi, Editor(s)

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