Statistical diagnostics to identify Galactic foregrounds in B-mode maps

Abstract

Recent developments in the search for inflationary gravitational waves in the cosmic microwave background (CMB) polarization motivate the search for new diagnostics to distinguish the Galactic foreground contribution to B modes from the cosmic signal. We show that B modes from these foregrounds should exhibit a local hexadecapolar departure in power from statistical isotropy (SI). We present a simple algorithm to search for a uniform SI violation of this sort, as may arise in a sufficiently small patch of sky. We then show how to search for these effects if the orientation of the SI violation varies across the survey region, as is more likely to occur in surveys with more sky coverage. If detected, these departures from Gaussianity would indicate some level of Galactic foreground contamination in the B-mode maps. Given uncertainties about foreground properties, though, caution should be exercised in attributing a null detection to an absence of foregrounds.

5 pages; version accepted to PRL

References in corpus (7)

• Toward an Understanding of Foreground Emission in the BICEP2 Region
• A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty
• Reconstructing Patchy Reionization from the Cosmic Microwave Background
• How to De-Rotate the Cosmic Microwave Background Polarization
• De-Rotation of the Cosmic Microwave Background Polarization: Full-Sky Formalism
• Constraining a spatially dependent rotation of the Cosmic Microwave Background Polarization
• Suzaku Studies of the Central Engine in the Typical Type I Seyfert NGC 3227: Detection of Multiple Primary X-ray Continua with Distinct Properties

Cited by in corpus (5)

• Inflationary cosmology in modified gravity theories
• Inflationary universe from perfect fluid and $F(R)$ gravity and its comparison with observational data
• Generation of large-scale magnetic fields, non-Gaussianity, and primordial gravitational waves in inflationary cosmology
• A Strategy to Minimize Dust Foregrounds in B-mode Searches
• B-modes and the sound speed of primordial fluctuations