An angular power spectrum analysis of the DRAO 1.4 GHz polarization survey: implications for CMB observations

Free access article

Issue		A&A Volume 455, Number 2, August IV 2006


Page(s)		L9 - L12
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20065535

A&A 455, L9-L12 (2006)
DOI: 10.1051/0004-6361:20065535

Letter

An angular power spectrum analysis of the DRAO 1.4 GHz polarization survey: implications for CMB observations

L. La Porta¹, C. Burigana², W. Reich¹ and P. Reich¹

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel, 69, 53121 Bonn, Germany
e-mail: laporta@mpifr-bonn.mpg.de
² INAF-IASF Bologna, via P. Gobetti, 101, 40129 Bologna, Italy

(Received 3 May 2006 / Accepted 1 June 2006 )

Abstract
Aims.The aim of the present analysis is to improve the knowledge of the statistical properties of the Galactic diffuse synchrotron emission, which constrains sensitive CMB anisotropy measurements.
Methods.We have analysed the new DRAO 1.4 GHz polarization survey together with the Stockert 1.4 GHz total intensity survey and derived the angular power spectra (APSs) of the total intensity, the polarized emission, and their cross-correlation for the entire surveys and for three low-intensity regions.
Results.The APSs of the diffuse synchrotron emission are modelled by power laws. For the E and B modes, a slope of $\alpha \sim [-3.0,-2.5]$ for the multipole range ~[30,300] is found. By the extrapolation of these results to 70 GHz, we can estimate the Galactic synchrotron contamination of CMB anisotropies, and we find results that are compatible with the ones coming from WMAP 3-yr data. In the low-intensity regions, the cosmological primordial B mode peak at $\ell \sim 100$ should be clearly observable for a tensor-to-scalar ratio $T/S \ga 0.5$ and a synchrotron temperature spectral index $\beta \sim -3$ . Its detection is also possible for $T/S \ga 0.005$ and $\beta \sim -3$ , in case a separation of the foreground from the CMB signal could be achieved with an accuracy of ~ $5{-}10\%$ . For the TE mode, a mask excluding $\vert b_{\rm gal}\vert \le 5^{\circ}$ (for $\beta\sim -3.0$ ) or $\vert b_{\rm gal}\vert \le 20^{\circ}$ (for $\beta\sim -2.8$ ) from the surveys is sufficient to render the foreground contamination negligible, thus confirming the ability of WMAP to have a clear view of the temperature-polarization correlation peak and antipeak series.

Key words: polarization -- Galaxy: general -- cosmology: cosmic microwave background -- methods: data analysis

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