2006MNRAS.367..132C

Polarized diffuse emission observations at 1.4 GHz in a high Galactic latitude area of the Northern celestial hemisphere are presented. The 3.2 x3.2deg² field, centred at RA = 10^h58^m, Dec. =+42°18' (B1950), has Galactic coordinates l∼ 172°, b∼+63° and is located in the region selected as northern target of the Balloon-borne Radiometers for Sky Polarization Observations experiment. Observations have been performed with the Effelsberg 100-m telescope. We find that the angular power spectra of the E and B modes have slopes of β_E=-1.79±0.13 and β_B=-1.74±0.12, respectively. Because of the very high Galactic latitude and the smooth emission, a weak Faraday rotation action is expected, which allows both a fair extrapolation to cosmic microwave background polarization (CMBP) frequencies and an estimate of the contamination by the Galactic synchrotron emission. We extrapolate the E-mode spectrum up to 32 GHz and confirm the possibility to safely detect the CMBP E-mode signal in the Ka band found in another low-emission region. Extrapolated up to 90 GHz, the Galactic synchrotron B mode looks to compete with the cosmic signal only for models with a tensor-to-scalar perturbation power ratio T/S < 0.001, which is even lower than the T/S value of 0.01 found to be accessible in the only other high Galactic latitude area investigated to date. This suggests that values as low as T/S= 0.01 might be accessed at high Galactic latitudes. Such low-emission values can allow a significant redshift of the best frequency to detect the CMBP B mode, also reducing the contamination by Galactic dust, and opening interesting perspectives to investigate inflation models.