MSc defense by Aske Gammelgaard Ravnebjerg

Properties of Polarized CMB Foreground Maps

Detecting the B-modes of the primordial polarized CMB is the smoking gun for the inflationary universe. Extracting the B-modes is particularly challenging and remains and ongoing effort. Strong diffuse polarized foregrounds in our galaxy contaminates the relatively weak B-mode signal, and a sufficient separation of the foreground components from the observed CMB sky is therefore required. The success of such a separation depends on the assumptions about the properties of foreground maps in component separation methods. The validity of the assumptions in the Internal Linear Combination (ILC) method is investigated using statistical methods on the E- and B-mode maps of polarized synchrotron- and thermal dust emission. Issues associated with the ILC method are highlighted, which in particular arise from spectral variance and noise properties of the foreground maps.