Foreground-Immune Cosmic Microwave Background Lensing with Shear-Only Reconstruction

Journal Article · Wed May 01 04:00:00 EDT 2019 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.122.181301· OSTI ID:1527182

Schaan, Emmanuel ^[1]; Ferraro, Simone ^[1]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States). Berkeley Center for Cosmological Physics

Cosmic microwave background (CMB) lensing from current and upcoming wide-field CMB experiments such as AdvACT, SPT-3G and Simons Observatory relies heavily on temperature (versus polarization). In this regime, foreground contamination to the temperature map produces significant lensing biases, which cannot be fully controlled by multifrequency component separation, masking, or bias hardening. In this Letter, we split the standard CMB lensing quadratic estimator into a new set of optimal “multipole” estimators. On large scales, these multipole estimators reduce to the known magnification and shear estimators, and a new shear B -mode estimator. We leverage the different symmetries of the lensed CMB and extragalactic foregrounds to argue that the shear-only estimator should be approximately immune to extragalactic foregrounds. We build a new method to compute, separately and without noise, the primary, secondary, and trispectrum biases to CMB lensing from foreground simulations. Using this method, we demonstrate that the shear estimator is, indeed, insensitive to extragalactic foregrounds, even when applied to a single-frequency temperature map contaminated with cosmic infrared background, thermal Sunyaev-Zel’dovich, kinematic Sunyaev-Zel’dovich, and radio point sources. This dramatic reduction in foreground biases allows us to include higher temperature multipoles than with the standard quadratic estimator, thus, increasing the total lensing signal-to-noise ratio beyond the quadratic estimator. In addition, magnification-only and shear B -mode estimators provide useful diagnostics for potential residuals.

• Research Organization: Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1527182
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 18 Vol. 122; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English