Reconstructing simulated CMB polarization power spectra with the Analytical Blind Separation method

TL;DR

This paper evaluates the Analytical Blind Separation (ABS) method's effectiveness in reconstructing CMB polarization power spectra from simulated multi-frequency sky maps, demonstrating good performance at smaller scales but highlighting challenges at larger scales.

Contribution

The study applies and tests the ABS method on simulated data for future space missions, analyzing its bias and performance in reconstructing CMB polarization spectra.

Findings

ABS performs well at intermediate and small scales despite foreground contamination.

Biases are present at large scales, requiring further mitigation.

Partial-sky analysis faces challenges due to E-B polarization confusion.

Abstract

Multi-frequency observations are needed to separate the CMB from foregrounds and accurately extract cosmological information from the data. The Analytical Blind Separation (ABS) method is dedicated to extracting the CMB power spectrum from multi-frequency observations in the presence of contamination from astrophysical foreground emission and instrumental noise. In this study, we apply the ABS method to simulated sky maps as could be observed with a future space-borne survey, in order to test the method's capability for determining the CMB polarization $E$- and $B$-mode power spectra. We present the ABS method performance on simulations for both a full-sky analysis and for an analysis concentrating on sky regions less impacted by Galactic foreground emission. We discuss the origin and minimization of biases in the estimated CMB polarization angular power spectra. We find that the ABS method performs quite well for the analysis of full-sky observations at intermediate and small angular scales, in spite of strong foreground contamination. On the largest scales, extra work is still required to reduce biases of various origins and the impact of confusion between CMB $E$ and $B$ polarization for partial-sky analyses.