Lensing bias to CMB polarization measurements of compensated isocurvature perturbations

Chen Heinrich
Phys. Rev. D 97, 023513 – Published 18 January 2018

Abstract

Compensated isocurvature perturbations (CIPs) are opposite spatial fluctuations in the baryon and dark matter (DM) densities. They arise in the curvaton model and some models of baryogenesis. While the gravitational effects of baryon fluctuations are compensated by those of DM, leaving no observable impacts on the cosmic microwave background (CMB) at first order, they modulate the sound horizon at recombination, thereby correlating CMB anisotropies at different multipoles. As a result, CIPs can be reconstructed using quadratic estimators similarly to CMB detection of gravitational lensing. Because of these similarities, however, the CIP estimators are biased with lensing contributions that must be subtracted. These lensing contributions for CMB polarization measurement of CIPs are found to roughly triple the noise power of the total CIP estimator on large scales. In addition, the cross power with temperature and E-mode polarization are contaminated by lensing-ISW (integrated Sachs-Wolfe) correlations and reionization-lensing correlations respectively. For a cosmic-variance-limited temperature and polarization experiment measuring out to multipoles lmax=2500, the lensing noise raises the detection threshold by a factor of 1.5, leaving a 2.7σ detection possible for the maximal CIP signal in the curvaton model.

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  • Received 4 September 2017

DOI:https://doi.org/10.1103/PhysRevD.97.023513

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Particles & FieldsGravitation, Cosmology & Astrophysics

Authors & Affiliations

Chen Heinrich*

  • Department of Physics, University of Chicago, Chicago, Illinois 60637, USA and Kavli Institute for Cosmological Physics, Enrico Fermi Institute, Chicago, Illinois 60637, USA

  • *chenhe@uchicago.edu

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Vol. 97, Iss. 2 — 15 January 2018

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