Lower bias, lower noise CMB lensing with foreground-hardened estimators

Journal Article · Tue Sep 15 00:00:00 EDT 2020 · Physical Review. D.

DOI:https://doi.org/10.1103/physrevd.102.063517· OSTI ID:1713255

Sailer, Noah ^[1]; Schaan, Emmanuel ^[2]; Ferraro, Simone ^[2]

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1. Univ. of California, Berkeley, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

Extragalactic foregrounds in temperature maps of the cosmic microwave background (CMB) severely limit the ability of standard estimators to reconstruct the weak lensing potential. These foregrounds are not fully removable by multifrequency cleaning or masking and can lead to large biases if not properly accounted for. For foregrounds made of a number of unclustered point sources, an estimator for the source amplitude can be derived and deprojected, removing any bias to the lensing reconstruction. We show with simulations that all of the extragalactic foregrounds in temperature can be approximated by a collection of sources with identical profiles, and that a simple bias hardening technique is effective at reducing any bias to lensing, at a minimal noise cost. In this work, we compare the performance and bias to other methods such as "shear-only" reconstruction, and discuss how to jointly deproject any arbitrary number of foregrounds, each with an arbitrary profile. In particular, for a Simons Observatory-like experiment foreground-hardened estimators allow us to extend the maximum multipole used in the reconstruction, increasing the overall statistical power by ~50% over the standard quadratic estimator, both in auto and cross-correlation. We conclude that source hardening outperforms the standard lensing quadratic estimator both in auto- A nd cross-correlation, and in terms of lensing signal-to-noise and foreground bias.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1713255
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 6 Vol. 102; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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