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PhysRevD.80.063004.pdf (2.04 MB)

Estimators for CMB Statistical Anisotropy

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journal contribution
posted on 2023-06-08, 05:29 authored by Duncan Hanson, Antony LewisAntony Lewis
We use quadratic maximum-likelihood (QML) estimators to constrain models with Gaussian but statistically anisotropic CMB fluctuations, using CMB maps with realistic sky-coverage and instrumental noise. This approach is optimal when the anisotropy is small, or when checking for consistency with isotropy. We demonstrate the power of the QML approach by applying it to the WMAP data to constrain several models which modulate the observed CMB fluctuations to produce a statistically anisotropic sky. We first constrain an empirically motivated spatial modulation of the observed CMB fluctuations, reproducing marginal evidence for a dipolar modulation pattern with amplitude 7% at l¿60, but demonstrate that the effect decreases at higher multipoles and is ¿1% at l~500. We also look for evidence of a direction-dependent primordial power spectrum, finding a very statistically significant quadrupole signal nearly aligned with the ecliptic plane; however we argue this anisotropy is largely contaminated by observational systematics. Finally, we constrain the anisotropy due to a spatial modulation of adiabatic and isocurvature primordial perturbations, and discuss the close relationship between anisotropy and non-Gaussianity estimators.

History

Publication status

  • Published

File Version

  • Published version

Journal

Physical Review D

ISSN

1050-2947

Issue

6

Volume

80

Page range

063004

Pages

15.0

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

First Open Access (FOA) Date

2016-03-22

First Compliant Deposit (FCD) Date

2016-11-10

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