Lens covariance effects on likelihood analyses of CMB power spectra

Abstract

Non-Gaussian correlations induced in CMB power spectra by gravitational lensing must be included in likelihood analyses for future CMB experiments. We present a simple but accurate likelihood model which includes these correlations and use it for Markov Chain Monte Carlo parameter estimation from simulated lensed CMB maps in the context of $\Lambda$CDM and extensions which include the sum of neutrino masses or the dark energy equation of state $w$. If lensing-induced covariance is not taken into account for a CMB-S4 type experiment, the errors for one combination of parameters in each case would be underestimated by more then a factor of two and lower limits on $w$ could be misestimated substantially. The frequency of falsely ruling out the true model or finding tension with other data sets would also substantially increase. Our analysis also enables a separation of lens and unlensed information from CMB power spectra, which provides for consistency tests of the model and, if combined with other such measurements, a nearly lens-sample-variance free test for systematics and new physics in the unlensed spectrum. This parameterization also leads to a simple effective likelihood that can be used to assist model building in case consistency tests of $\Lambda$CDM fail.

arXiv comment19 pages, 23 figures

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Cited by in corpus (5)

• The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz
• Tensions between direct measurements of the lens power spectrum from Planck data
• Lensing-like tensions in the Planck legacy release
• Likelihood methods for CMB experiments
• Lensing covariance on cut sky and SPT-Planck lensing tensions