Impact of polarized galactic foreground emission on CMB lensing reconstruction and delensing of B-modes

Abstract

Next generation CMB experiments such as CMB-S4 aim at measuring the CMB lensing potential at sub-percent precision where most of the constraining power will come from CMB polarization. We investigate the prospects of achieving this goal in the presence of large-scale, diffuse galactic foreground emission by using non-Gaussian sky simulations and exploit multi-frequency information to clean those. We show that, while prior to foreground cleaning, cosmological parameter estimates from the contaminated lensing potential estimation with the quadratic estimator can be significantly biased, these can be successfully mitigated by applying a parametric foreground cleaning approach. We further observe no significant additional bias in the delensed B-mode power spectrum after applying foreground cleaning and are therefore able to obtain an unbiased measurement of the tensor-to-scalar ratio, r, after delensing with the quadratic estimate of the lensing potential.

Full-sky, arcminute-scale, 3D models of Galactic microwave foreground dust emission based on filaments

“…Recent works have looked at the impact of foregrounds on the small-scale lensing reconstruction, and in particular the effect of non-Gaussian foreground residuals (e.g. Beck et al 2020;Baleato Lizancos et al 2021). One feature of our model is its ability to fine-tune the non-Gaussianity by increasing or decreasing the density of filaments or changing the filament profile.…”

MillimeterDL: Deep Learning Simulations of the Microwave Sky

“…There have also been a number of efforts to simulate Galactic foregrounds in both intensity and polarization [35][36][37][38][39][40][41][42][43]. Modeling the small-scale features of Galactic foregrounds is particularly challenging given the current lack of observations on comparable scales in millimeter wavebands, though there is progress in this direction [44].…”

CMB lensing reconstruction biases from masking extragalactic sources

“…For near-future observations, such as SO, the temperature signal still contains a substantial fraction of the available information, so fully exploiting the data will require robust modelling of the temperature signal, which is what we focus on in this work. The contamination induced by foregrounds is less important for CMB lensing reconstruction using polarization [48], since the polarized foreground amplitudes are expected to be substantially lower, but should also be assessed in future work (future observations by CMB-S4 [49, S4 hereafter] will give lensing reconstructions that are more dominated by polarization).…”