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Issue A&A
Volume 484, Number 3, June IV 2008
Page(s) 733 - 742
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20078842
Published online 08 April 2008



A&A 484, 733-742 (2008)
DOI: 10.1051/0004-6361:20078842

A fully sampled $\lambda$21 cm linear polarization survey of the southern sky

J. C. Testori1, 2, P. Reich1, and W. Reich1

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: wreich@mpifr-bonn.mpg.de
2  Instituto Argentino de Radioastronomiá, C.C.5 (1894) Villa Elisa, Argentina

Received 12 October 2007 / Accepted 25 February 2008

Abstract
Context. Linear polarization of Galactic synchrotron emission provides valuable information on the Galactic magnetic field and on the properties of the Galactic magneto-ionic medium. Polarized high-latitude Galactic emission is the major foreground for polarization studies of the cosmic microwave background.
Aims. We present a new southern-sky $\lambda$21 cm linear polarization survey, which complements the recent $\lambda$21 cm DRAO northern sky polarization data.
Methods. We used a 30-m telescope located at Villa Elisa/Argentina to map the southern sky simultaneously in continuum and linear polarization.
Results. We present a fully sampled map of linearly polarized emission at $\lambda$21 cm of the southern sky for declinations between -10° and -90°. The angular resolution of the survey is 36' and its sensitivity is 15 mK (rms-noise) in Stokes U and Q. The survey's zero-level has been adjusted to that of the recent DRAO 1.4 GHz linear polarization survey by comparing data in the region of overlap between -10° and -27°.
Conclusions. The polarized southern sky at 1.4 GHz shows large areas with smooth low-level emission almost uncorrelated to total intensities indicating that Faraday rotation originating in the Galactic interstellar medium along the line of sight is significant at 1.4 GHz. The southern sky is much less contaminated by local foreground features than is the northern sky. Thus high-frequency observations of polarized cosmic microwave emission are expected to be less affected. The percentage polarization of the high-latitude emission is low, which seems to be an intrinsic property of Galactic emission.


Key words: polarization -- radiation mechanisms: non-thermal -- ISM: magnetic fields



© ESO 2008


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