High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

We analyse the polarized emission at 1.4 GHz in a 3 degrees x 3 degrees area at high Galactic latitude (b similar to -40 degrees). The region, centred in (alpha = 5(h), delta = -49 degrees), was observed with the Australia Telescope Compact Array (ATCA) radio-interferometer, whose 3-30 arcmin angular sensitivity range allows the study of scales appropriate for cosmic microwave background polarization (CMBP) investigations. The angular behaviour of the diffuse emission is analysed through the E- and B-mode angular power spectra. These follow a power law C-l(x) proportional to lB(X) with slopes beta(E =) -1.97 +/- 0.08 and beta(B) = -1.98 +/- 0.07. The emission is found to be approximately a factor 25 fainter than in Galactic plane regions. The comparison of the power spectra with other surveys indicates that this area is intermediate between strong and negligible Faraday rotation effects. A similar conclusion can be reached by analysing both the frequency and Galactic latitude behaviours of the diffuse Galactic emission of the 408-1411 MHz Leiden survey data. We present an analysis of the Faraday rotation effects on the polarized power spectra and find that the observed power spectra can be enhanced by a transfer of power from large to small angular scales. The extrapolation of the spectra to 32 and 90 Ghz of the cosmic microwave background (CMB) window suggest that Galactic synchrotron emission leaves the CMBP be more than 4 orders of magnitude below the CMBP spectrum. Extrapolating to the relevant models with tensor-scalar fluctuation power ratio T/S > 0.01. We also identify polarized point sources in the field, providing a nine object list, which is complete down to the polarized flux limit of S-lim(p) = 2 mJy.