Combining ILC and moment expansion techniques for extracting average-sky signals and CMB anisotropies

Understand

The method of weighted addition of multi-frequency maps, more commonly referred to as {\it Internal Linear Combination} (ILC), has been extensively employed in the measurement of cosmic microwave background (CMB) anisotropies and its secondaries along with similar application in 21cm data analysis.

• Here we argue and demonstrate that ILC methods can also be applied to data from absolutely-calibrated CMB experiments to extract average-sky signals in addition to the conventional CMB anisotropies.
• The performance of the simple ILC method is, however, limited, but can be significantly improved by adding constraints informed by physics and existing empirical information.
• In recent work, a moment description has been introduced as a technique of carrying out high precision modeling of foregrounds in the presence of inevitable averaging effects.