The impact of extragalactic foregrounds on internal delensing of CMB B-mode polarization

Understand

The search for primordial $B$-mode polarization of the CMB is limited by the sample variance of $B$-modes produced at later times by gravitational lensing.

• Constraints can be improved by `delensing': using some proxy of the matter distribution to partially remove the lensing-induced $B$-modes.
• Current and soon-upcoming experiments will infer a matter map -- at least in part -- from the temperature anisotropies of the CMB.
• These reconstructions are contaminated by extragalactic foregrounds: radio-emitting galaxies, the cosmic infrared background, or the Sunyaev--Zel'dovich effects.