Model independent variance cancellation in CMB lensing cross-correlations

Abstract

Cross-correlations of CMB lensing reconstructions with other tracers of matter constrain primordial non-Gaussianity, neutrino masses and structure growth as a function of cosmic time. We formalize a method to improve the precision of these measurements by using a third tracer to remove structure from the lensing reconstructions. Crucially, our method enjoys the variance reduction benefits of a joint-modelling approach without the need to model the cosmological dependence of the ancillary tracer. We present a first demonstration of variance cancellation using data from Planck and the DESI Legacy Surveys, showing a 10-20% reduction in both lensing power and cross-correlation variance using the Cosmic Infrared Background (CIB) or DESI Legacy Survey Luminous Red Galaxies (LRGs) as matter tracers.

6 pages of main text + 6 pages of appendices + bibliography. 6 figures. Minor changes to match version published in PRD

References in corpus (5)

• SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope
• CMB lensing from Planck PR4 maps
• DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
• Target Selection and Validation of DESI Luminous Red Galaxies
• The Target-selection Pipeline for the Dark Energy Spectroscopic Instrument

Cited by in corpus (2)

• Removal of interloper contamination to line-intensity maps using correlations with ancillary tracers of the large-scale structure
• Delensing CMB B-modes using galaxy surveys: the effect of galaxy bias and matter clustering non-linearities