Efficient ILC analysis on polarization maps after EB leakage correction

Abstract

The Internal Linear Combination (ILC) is widely used to extract the cosmic microwave background (CMB) signal from multi-frequency observation maps, especially for Satellite experiments with quasi-full sky coverage. We extend ILC method to CMB polarization map analysis with a small sky patch which is especially typical for ground-based experiments, by combing ILC with a template cleaning method which can give pure B map free from EB leakage caused by partial sky coverage. The feature of our methods is that we do the ILC analysis on pseudo-scalar B maps, and the advantage is that it totally avoids the impact of EB leakage on ILC, so that it can improve the efficiency of component separation dramatically. We demonstrate our methods with mock data of a future ground-based experiment with a deep survey on a clean patch in the northern sky, and the results show that the level of foreground residual can be well controlled, it biases the tensor to scalar ratio (r) at the order of 10-3 which is comparable to the statistical error by noise.