Fluctuations in the galactic synchrotron radiation. I - Implications for searches for fluctuations of cosmological origin

The likely contribution of galactic synchrotron radiation (GSR) to the apparent anisotropies of the Cosmic Microwave Background radiation (CMB) is reviewed. A 'GSR-quiet' region of the sky is identified at delta = 40 deg, RA = 180-250 deg, which coincides with the region where Davies et al. (1987) and Watson (1989) have claimed tentative evidence for detection of an anisotropy. By considering the nature of the GSR in this region, it is concluded that this excess can very probably be accounted for by galactic emission rather than bona fide CMB anisotropies. From the increased understanding of the structure of the GSR, there is hope for genuine detections in higher frequency observations.