General Seminar

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General Seminar takes place every Monday at 11.15 in Piwnice, radioastronomy seminar room.
Remote participation via the BigBlueButton (BBB).

13 April 2026

“Challenges for CMB B modes: Lensing Reconstruction, Subtraction, and Diffuse Foregrounds”

mgr Kishan Deka
The National Centre for Nuclear Research

Abstract:
In the era of high precision Cosmic Microwave Background (CMB) anisotropy measurements, detection of the primordial gravitational waves (PGW) will be one of the main goals of the upcoming CMB experiments. To make it possible, precise cleaning of the CMB polarisation maps from diffused contamination coming from polarised galactic emission and CMB gravitational lensing effect is needed. We investigate the impact of residual galactic foregrounds in lensing reconstruction and delensing of B modes for stage-4 CMB experiments. In this work, we pay special attention to forecast constraints for the amplitude of the primordial gravitational waves and their sensitivity to different foreground models with varying complexity. We are currently exploring a tomographic delensing method on simulations of LSST and Simons Observatory. We aim to achieve optimal delensing efficiency by using a multi-tracer approach, where we split the LSST observations into tomographic redshift bins. We aim to understand the impact of photometric redshift bin mismatch error on the estimation of primordial gravity wave amplitude.