CMB foregrounds - A brief review

TL;DR

This review discusses the challenges posed by foreground radiation in CMB observations, emphasizing the importance of component separation techniques for accurate polarization measurements, especially for detecting inflationary B-modes.

Contribution

It provides a concise overview of CMB foregrounds, highlighting the complexities in polarization and the necessity of advanced component separation for future missions.

Findings

Foregrounds are complex but manageable in temperature measurements.

Polarized Galactic radiation significantly complicates B-mode detection.

Multi-frequency component separation is essential for minimizing foreground errors.

Abstract

CMB foregrounds consist of all radiation between the surface of last scattering and the detectors, which can interfere with the cosmological interpretation of CMB data. Fortunately, in temperature (intensity), even though the foregrounds are complex they can relatively easily be mitigated. However, in polarization, diffuse Galactic radiation (synchrotron and thermal dust) can be polarized at a level of >10 % making it more of a challenge. In particular, CMB B-modes, which are a smoking-gun signature of inflation, will be dominated by foregrounds. Component separation will therefore be critical for future CMB polarization missions, requiring many channels covering a wide range of frequencies, to ensure that foreground modelling errors are minimised.