Recovering hidden signals of statistical anisotropy from a masked or partial CMB sky

TL;DR

This paper presents a bipolar spherical harmonic method to recover hidden anisotropic signals in CMB data, effectively addressing masking effects and demonstrated by recovering Doppler boost signals from simulated skies.

Contribution

It introduces a generic BipoSH-based procedure to disentangle masking-induced correlations from true anisotropic signals in CMB maps.

Findings

Successfully recovers Doppler boost signals from simulated CMB skies.

Addresses masking effects to improve anisotropy detection.

Applicable to various isotropy-violating phenomena.

Abstract

Any isotropy violating phenomena on cosmic microwave background (CMB) induces off-diagonal correlations in the two-point function. These correlations themselves can be used to estimate the underlying anisotropic signals. Masking due to residual foregrounds, or availability of partial sky due to survey limitation, are unavoidable circumstances in CMB studies. But, masking induces additional correlations, and thus complicates the recovery of such signals. In this work, we discuss a procedure based on bipolar spherical harmonic (BipoSH) formalism to comprehensively addresses any spurious correlations induced by masking and successfully recover hidden signals of anisotropy in observed CMB maps. This method is generic, and can be applied to recover a variety of isotropy violating phenomena. Here, we illustrate the procedure by recovering the subtle Doppler boost signal from simulated boosted CMB skies, which has become possible with the unprecedented full-sky sensitivity of PLANCK probe.