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

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 α ∼ [−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 ∼ 100 should be clearly observable for a tensor-to-scalar ratio T/S > ∼ 0.5 and a synchrotron temperature spectral index β ∼ −3. Its detection is also possible for T/S > ∼ 0.005 and β ∼ −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 |b gal | ≤ 5• (for β ∼ −3.0) or |b gal | ≤ 20• (for β ∼ −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.

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

“…The CMB C TB l and C EB l are expected for most cosmological models to be null and therefore, the foregrounds contribution dominates the signal. These results are consistent with previous estimates by La Porta et al (2006) who considered only synchrotron emission and with those of Ponthieu et al (2005) who modeled only the dust emission.…”

B-mode contamination by synchrotron emission from 3-yr Wilkinson Microwave Anisotropy Probe data

“…These authors use about 75 per cent of the sky (all high latitudes but strong large local structures like the Northern Galactic Spur) and find that at 60–70 GHz the synchrotron emission competes with the cosmic B ‐mode signal even for models with T / S = 0.3–0.5, which are already disfavoured by the present upper limits. Similar results are obtained by La Porta et al (2006) through the analysis of the 1.4‐GHz sky at latitude | b | > 20° using the Dominion Radio Astrophysical Observatory (DRAO) survey data (Wolleben et al 2006).…”

A fully sampled λ21 cm linear polarization survey of the southern sky

“…The southern sky is therefore better-suited for studies of the large-scale polarized cosmic microwave background than the northern sky. La Porta (2007) has made a comparative analysis of the angular power spectra of both the northern polarized sky (La Porta et al 2006) and the southern polarized sky, and it reveals differences due to the local structures in the northern sky, which have an influence for latitudes of up to about 60…”