Extended Delta-map: a map-based foreground removal method for CMB polarization observations

TL;DR

This paper introduces an extended delta-map method for CMB polarization foreground removal, allowing the use of arbitrary observation bands to improve sensitivity to inflationary gravitational waves.

Contribution

The authors extend the delta-map method to handle any number of observation bands, enhancing sensitivity in detecting primordial B-mode signals.

Findings

Method can incorporate multiple observation bands.

Improves sensitivity to tensor-to-scalar ratio r.

No significant bias introduced in results.

Abstract

In order to extract information about inflationary gravitational waves using $B$-mode patterns of cosmic microwave polarization anisotropy, we need to remove the foreground radiation from the Milky Way. In our previous delta-map method for foreground removal, the number of observation bands was limited to the number of parameters of the assumed foreground model, and therefore it was difficult to improve the sensitivity by increasing the number of observation bands. Here, we extend the previous method so that it can be adapted to an arbitrary number of observation bands. Using parametric likelihood and realistic foreground and CMB simulations, we show that our method can increase the sensitivity to the tensor-to-scalar ratio $r$ without inducing any significant bias.