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Accurate foreground characterisation for future CMB experiments

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A clear view of 'relic' radiation

An EU-funded project worked to remove any sources of diffuse foreground emission from cosmic microwave background (CMB) observations.

Climate Change and Environment

Understanding and measuring astrophysical foreground emission, such as diffuse galactic emission, has become an important topic in CMB data analysis. Future, ultra-sensitive CMB experiments are expected to detect polarised gravitational waves arising from cosmic inflation. However, their B-mode polarisation is very weak and requires precision greater than 1 microkelvin. The EU-funded project 'Accurate foreground characterisation for future CMB experiments' (CMBFOREGROUNDS) played a major role in using observations and data analyses from several CMB/foreground experiments. Its aim was to measure and remove foreground emissions, which required combining data from multiple instruments to obtain reliable B-mode measurements. CMBFOREGROUNDS had the necessary background (from other projects in which the coordination institution was involved) to understand ground spillover, which is a major limitation for producing polarisation maps. Based on some first CMB maps showing the faint synchrotron emission, the project sought to also provide reliable ones for the coming two years. A paper was prepared that contained a first analysis of the main diffuse galactic foreground components by combining the latest full-sky microwave surveys.

Keywords

Foreground emission, cosmic microwave background, diffuse galactic emission, gravitational wave, cosmic inflation, B-mode measurement, polarisation map, faint synchrotron emission

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