Lensing Bias to CMB Measurements of Compensated Isocurvature Perturbations

Abstract

Compensated isocurvature perturbations (CIPs) are modes in which the baryon and dark matter density fluctuations cancel. They arise in the curvaton scenario as well as some models of baryogenesis. While they leave no observable effects on the cosmic microwave background (CMB) at linear order, they do spatially modulate two-point CMB statistics and can be reconstructed in a manner similar to gravitational lensing. Due to the similarity between the effects of CMB lensing and CIPs, lensing contributes nearly Gaussian random noise to the CIP estimator that approximately doubles the reconstruction noise power. Additionally, the cross correlation between lensing and the integrated Sachs-Wolfe (ISW) effect generates a correlation between the CIP estimator and the temperature field even in the absence of a correlated CIP signal. For cosmic-variance limited temperature measurements out to multipoles $l\le 2500$, subtracting a fixed lensing bias degrades the detection threshold for CIPs by a factor of $1.3$, whether or not they are correlated with the adiabatic mode.

10 pages, 12 figures; one of the authors Chen He Heinrich was previously known as Chen He

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• Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature
• Responses of Halo Occupation Distributions: a new ingredient in the halo model & the impact on galaxy bias
• Probing spatial variation of the fine-structure constant using the CMB
• Compensated Isocurvature Perturbations in the Galaxy Power Spectrum
• BAO Modulation as a Probe of Compensated Isocurvature Perturbations
• Uncorrelated Compensated Isocurvature Perturbations from kSZ Tomography
• Isocurvature initial conditions for second order Boltzmann solvers
• Magnetic Fields from Compensated Isocurvature Perturbations
• Lensing Bias to CMB Polarization Measurements of Compensated Isocurvature Perturbations
• Non-linear effects in early Universe cosmology
• The intrinsic bispectrum of the CMB from isocurvature initial conditions