Foreground-immune CMB lensing reconstruction with polarization

Abstract

Extragalactic foregrounds are known to generate significant biases in temperature-based CMB lensing reconstruction. Several techniques, which include ``source hardening'' and ``shear-only estimators'' have been proposed to mitigate contamination and have been shown to be very effective at reducing foreground-induced biases. Here we extend both techniques to polarization, which will be an essential component of CMB lensing reconstruction for future experiments, and investigate the ``large-lens'' limit analytically to gain insight on the origin and scaling of foreground biases, as well as the sensitivity to their profiles.Using simulations of polarized point sources, we estimate the expected bias to both Simons Observatory and CMB-S4 like (polarization-based) lensing reconstruction, finding that biases to the former are minuscule while those to the latter are potentially non-negligible at small scales ($L\sim 1000-2000$). In particular, we show that for a CMB-S4 like experiment, an optimal linear combination of point-source hardened estimators can reduce the (point-source induced) bias to the CMB lensing power spectrum by up to two orders of magnitude, at a $\sim 4\%$ noise cost relative to the global minimum variance estimator.

arXiv commentpublished in PRD; 18 pages, 7 figures

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• The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth
• The Atacama Cosmology Telescope: Cosmology from cross-correlations of unWISE galaxies and ACT DR6 CMB lensing
• The Atacama Cosmology Telescope DR6 and DESI: Structure formation over cosmic time with a measurement of the cross-correlation of CMB Lensing and Luminous Red Galaxies
• Cosmological constraints from the cross-correlation of DESI Luminous Red Galaxies with CMB lensing from Planck PR4 and ACT DR6
• LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing
• Robust and efficient CMB lensing power spectrum from polarization surveys
• Real-world CMB lensing quadratic estimator power spectrum response
• CMB lensing with shear-only reconstruction on the full sky
• LiteBIRD Science Goals and Forecasts: A full-sky measurement of gravitational lensing of the CMB
• Unveiling Neutrino Halos with CMB Lensing
• The reconstructed CMB lensing bispectrum
• CMB lensing power spectrum without noise bias
• New probe of inflationary gravitational waves: cross-correlations of lensed primary CMB B-modes with large-scale structure
• Impact of Galactic non-Gaussian foregrounds on CMB lensing measurements
• The Atacama Cosmology Telescope: A demonstration of CMB lensing measurement from daytime data
• Mitigating point-source contamination in CMB polarization: a Generalized Point Spread Function fitting approach