BeyondPlanck VIII. Efficient Sidelobe Convolution and Correction through Spin Harmonics

Abstract

We introduce a new formulation of the Conviqt convolution algorithm in terms of spin harmonics, and apply this to the problem of sidelobe correction for BeyondPlanck, the first end-to-end Bayesian Gibbs sampling framework for CMB analysis. We compare our implementation to the previous Planck LevelS implementation, and find good agreement between the two codes in terms of accuracy, but with a speed-up reaching a factor of 3--10, depending on the frequency bandlimits, $l_{\text{max}}$ and $m_{\text{max}}$. The new algorithm is significantly simpler to implement and maintain, since all low-level calculations are handled through an external spherical harmonic transform library. We find that our mean sidelobe estimates for Planck LFI agree well with previous efforts. Additionally, we present novel sidelobe rms maps that quantify the uncertainty in the sidelobe corrections due to variations in the sky model.

9 pages, 8 figures. Part of the BeyondPlanck paper suite

References in corpus (6)

• Planck intermediate results. LVII. Joint Planck LFI and HFI data processing
• On the proper kinetic quadrupole CMB removal and the quadrupole anomalies
• BeyondPlanck I. Global Bayesian analysis of the Planck Low Frequency Instrument data
• BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and priors
• BeyondPlanck VII. Bayesian estimation of gain and absolute calibration for CMB experiments
• From BeyondPlanck to Cosmoglobe: Preliminary $WMAP$ $Q$-band analysis

Cited by in corpus (8)

• Improved cosmic microwave background (de-)lensing using general spherical harmonic transforms
• BeyondPlanck I. Global Bayesian analysis of the Planck Low Frequency Instrument data
• BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and priors
• BeyondPlanck XI. Bayesian CMB analysis with sample-based end-to-end error propagation
• From BeyondPlanck to Cosmoglobe: Preliminary $WMAP$ $Q$-band analysis
• Cosmoglobe DR1 results. I. Improved Wilkinson Microwave Anisotropy Probe maps through Bayesian end-to-end analysis
• BeyondPlanck XVI. Limits on Large-Scale Polarized Anomalous Microwave Emission from Planck LFI and WMAP
• BeyondPlanck X. Planck LFI frequency maps with sample-based error propagation