The power-law behaviours of angular spectra of polarized Galactic synchrotron
Abstract
We study the angular power spectra of polarized Galactic synchrotron in the range 10<l<800, at several frequencies between 0.4 and 2.7 GHz and at several Galactic latitudes up to near the North Galactic Pole. Electric- and magnetic-parity polarization spectra are found to have slopes around alpha E,B = 1.4 - 1.5 in the Parkes and Effelsberg Galactic-Plane surveys, but strong local fluctuations of alphaE,B are found at | b | ~ 10 degree from the 1.4 GHz Effelsberg survey. The CPIl spectrum, which is insensitive to the polarization direction, is somewhat steeper, being alphaPI = 1.6 - 1.8 for the same surveys. The low-resolution multifrequency survey of Brouw and Spoelstra (1976) shows some flattening of the spectra below 1 GHz, more intense for CE,Bl than for CPIl. In no case we find evidence for really steep spectra. The extrapolation to the cosmological window shows that at 90 GHz the detection of E-mode harmonics in the cosmic background radiation should not be disturbed by synchrotron, even around l~10 for a reionization optical depth tau ri>~0.05.
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