Circular polarization of the CMB: Foregrounds and detection prospects

Understand

The cosmic microwave background (CMB) is one of the finest probes of cosmology.

• Its all-sky temperature and linear polarization (LP) fluctuations have been measured precisely at a level of deltaT/TCMB ~10^{-6}.
• In comparison, circular polarization (CP) of the CMB, however, has not been precisely explored.
• Current upper limit on the CP of the CMB is at a level of deltaV/TCMB ~10^{-4} and is limited on large scales.