Polarized CMB Foregrounds: What do we know and how bad is it?

TL;DR

This paper reviews the current understanding of polarized foregrounds affecting CMB B-mode detection, highlighting challenges and potential for future detection of primordial signals.

Contribution

It provides an overview of polarized foregrounds, their impact on CMB B-mode searches, and assesses the feasibility of detecting primordial signals amidst these foregrounds.

Findings

Galactic synchrotron emission dominates at low frequencies.

Radio sources contribute significantly on large scales.

Detection of r=0.001 may be possible if foreground complexity is manageable.

Abstract

Polarized foregrounds are going to be a serious challenge for detecting CMB cosmological B-modes. Both diffuse Galactic emission and extragalactic sources contribute significantly to the power spectrum on large angular scales. At low frequencies, Galactic synchrotron emission will dominate with fractional polarization $\sim 20-40%$ at high latitudes while radio sources can contribute significantly even on large ($\sim 1^{\circ}$) angular scales. Nevertheless, simulations suggest that a detection at the level of $r=0.001$ might be achievable if the foregrounds are not too complex.