Speaker
Description
Detection of a divergence-free (B-mode) component in the primary CMB polarisation field will provide direct evidence of inflationary primordial gravitational waves (PGWs) in the early universe. However, weak gravitational lensing of CMB photons due to intervening mass distributions of the Universe distorts the primordial polarisation patterns, introducing an additional lensing-induced B-mode signal. Removing these lensing-induced B-modes is essential for improving constraints on the amplitude of PGWs. One main challenge in doing that is the contamination from polarised Galactic foregrounds that increase the variance of the polarisation maps. In our work, we tested the impact of residual foreground contamination for varying complexity of foreground models and quantified its contribution to the uncertainty in the primordial gravity wave constraint. Additionally, we explored the possibility to include other large-scale structure tracers such as galaxy overdensity maps in order to improve the de-lensing efficiency. We studied the combined impact of Galactic foreground residuals and photometric redshift errors in the context of upcoming CMB and galaxy-survey datasets from the Simons Observatory and the Rubin Observatory, respectively.
