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Measurement of the Crab nebula polarization at 90 GHz as a calibrator for CMB experiments | | J. Aumont
; L. Conversi
; E. Falgarone
; J. F. Macias-Perez
; F. Piacentini
; E. Pointecouteau
; N. Ponthieu
; J. L. Puget
; C. Rosset
; C. Thum
; M. Tristram
; H. Wiesemeyer
; | | Date: |
9 Dec 2009 | | Abstract: | CMB experiments aiming at a precise measurement of the CMB polarization, such
as the Planck satellite, need a strong polarized absolute calibrator on the sky
in order to accurately set the detectors polarization angle and the
cross-polarization leakage. The Crab Nebula, as the most intense polarized
source in the microwave sky at angular scales of few arcminutes, will be used
for this purpose. Our goal was to measure the Crab nebula polarization
characteristics at 90 GHz with an unprecedented precision. The observations
were carried out with the IRAM 30m telescope employing the correlation
polarimeter XPOL and using two orthogonally polarized receivers. We have
processed the Stokes I, Q and U maps from our observations in order to compute
the polarization angle and linear polarization fraction. The first is almost
constant in the region of maximum emission in polarization with a mean value of
alpha_Sky=152.1+/-0.2 deg and the second is found to reach a maximum of Pi=30%
for the most polarized pixels. We find that a CMB experiment having a 5 arcmin
circular beam will see a mean polarization angle of alpha_Sky=149.9+/-0.2 deg
and a mean polarization fraction of Pi=8.8+/-0.2%. | | Source: | arXiv, 0912.1751 | | Services: | Forum | Review | PDF | Favorites | |
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