Quantifying bias due to non-Gaussian foregrounds in an optimal reconstruction of CMB lensing and temperature power spectra

We estimate the magnitude of the bias due to non-Gaussian extragalactic foregrounds on the optimal reconstruction of the cosmic microwave background (CMB) lensing potential and temperature power spectra. The reconstruction is performed using a Bayesian inference method known as the marginal unbiased score expansion (MUSE). We apply MUSE to a minimum variance combination of multifrequency maps drawn from the Agora publicly available simulations of the lensed CMB and correlated extragalactic foreground emission. Taking noise levels appropriate to the SPT-3G D1 release, we find non-Gaussian foregrounds may bias the MUSE reconstruction of the lensing potential amplitude at the level of (0.7 ± 0.3)σ when using modes up to ℓ_max = 3500. We do not detect a statistically significant bias, finding a value of (-0.4 ± 0.3)σ, when restricted to lower angular multipoles, ℓ_max = 3000. This work is a first step toward understanding the impact of extragalactic foregrounds on optimal reconstructions of CMB temperature and lensing potential power spectra.. Authors: Doohan, M. [Univ. of Melbourne, Parkville, VIC (Australia)] (ORCID:0000000221950617); Millea, Marius [Univ. of California, Davis, CA (United States)] (ORCID:0000000173170551); Raghunathan, S. [Univ. of Illinois at Urbana-Champaign, IL (United States). National Center for Supercomputing Applications (NCSA)] (ORCID:000000031405378X); Ge, F. [Univ. of California, Davis, CA (United States)] (ORCID:0000000238338133); Knox, L. [Univ. of California, Davis, CA (United States)]. DOE Contract: AC02-76SF00515. Subjects: Statistical sampling techniques; non-gaussianity; weak gravitational lensing