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Advances in Astronomy
Volume 2012 (2012), Article ID 624987, 17 pages
Research Article

The Impact of Polarized Extragalactic Radio Sources on the Detection of CMB Anisotropies in Polarization

1LAL, Université Paris-Sud and CNRS/IN2P3, 91400 Orsay, France
2Departamento de Física, Universidad de Oviedo, C. Calvo Sotelo s/n, 33007 Oviedo, Spain
3IFCA, Universidad de Cantabria, Avenida los Castros s/n, 39005 Santander, Spain

Received 1 December 2011; Revised 21 March 2012; Accepted 2 April 2012

Academic Editor: Carlo Burigana

Copyright © 2012 Marco Tucci and Luigi Toffolatti. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Recent polarimetric surveys of extragalactic radio sources (ERS) at frequencies ν1 GHz are reviewed. By exploiting all the most relevant data we study the frequency dependence of polarization properties of ERS between 1.4 and 86 GHz. For flat-spectrum sources the median (mean) fractional polarization increases from 1.5% (2–2.5%) at 1.4 GHz to 2.5–3% (3–3.5%) at ν>10 GHz. Steep-spectrum sources are typically more polarized, especially at high frequencies where Faraday depolarization is less relevant. Current data suggest that at high radio frequencies (ν20) GHz the fractional polarization of ERS does not depend on total flux density and moderately increases with frequency. We estimate ERS number counts in polarization and the contribution of unresolved polarized ERS to angular power spectra. A first application is for the Planck satellite mission: we predict that only a dozen polarized ERS will be detected by the Planck LFI, and a few tens by the HFI. As for CMB power spectra, ERS should not be a strong contaminant to the CMB E-mode polarization at ν70 GHz, but they can become a relevant constraint for the detection of the cosmological B-mode polarization if the tensor-to-scalar ratio is 0.01.