Low-l CMB Analysis and Inpainting

TL;DR

This paper evaluates and compares three novel inpainting methods for reconstructing low-multipole CMB spherical harmonic coefficients in masked regions, achieving near cosmic variance accuracy for large sky masks.

Contribution

Introduces three new inpainting techniques based on sparsity, energy, and isotropy priors, demonstrating their effectiveness in high-quality CMB reconstruction.

Findings

Sparsity and energy priors achieve reconstruction within 1% of cosmic variance.

Two methods outperform existing approaches for large sky masks.

High-fidelity recovery of low-$$ coefficients demonstrated.

Abstract

Reconstruction of the CMB in the Galactic plane is extremely difficult due to the dominant foreground emissions such as Dust, Free-Free or Synchrotron. For cosmological studies, the standard approach consists in masking this area where the reconstruction is not good enough. This leads to difficulties for the statistical analysis of the CMB map, especially at very large scales (to study for e.g., the low quadrupole, ISW, axis of evil, etc). We investigate in this paper how well some inpainting techniques can recover the low-$\ell$ spherical harmonic coefficients. We introduce three new inpainting techniques based on three different kinds of priors: sparsity, energy and isotropy, and we compare them. We show that two of them, sparsity and energy priors, can lead to extremely high quality reconstruction, within 1% of the cosmic variance for a mask with Fsky larger than 80%.