SILC: a new Planck Internal Linear Combination CMB temperature map using directional wavelets

Abstract

We present new clean maps of the CMB temperature anisotropies (as measured by Planck) constructed with a novel internal linear combination (ILC) algorithm using directional, scale-discretised wavelets --- Scale-discretised, directional wavelet ILC or SILC. Directional wavelets, when convolved with signals on the sphere, can separate the anisotropic filamentary structures which are characteristic of both the CMB and foregrounds. Extending previous component separation methods, which use the frequency, spatial and harmonic signatures of foregrounds to separate them from the cosmological background signal, SILC can additionally use morphological information in the foregrounds and CMB to better localise the cleaning algorithm. We test the method on Planck data and simulations, demonstrating consistency with existing component separation algorithms, and discuss how to optimise the use of morphological information by varying the number of directional wavelets as a function of spatial scale. We find that combining the use of directional and axisymmetric wavelets depending on scale could yield higher quality CMB temperature maps. Our results set the stage for the application of SILC to polarisation anisotropies through an extension to spin wavelets.

15 pages, 13 figures. Minor changes to match version published in MNRAS. Map products available at http://www.silc-cmb.org

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Cited by in corpus (16)

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• An Improved Diffuse Foreground Subtraction by ILC method: CMB Map and Angular Power Spectrum using Planck and WMAP Observations
• Spin-SILC: CMB polarisation component separation with spin wavelets
• Sparse image reconstruction on the sphere: analysis and synthesis
• The cosmic microwave background Cold Spot anomaly: the impact of sky masking and the expected contribution from the Integrated Sachs-Wolfe effect
• A Novel CMB Component Separation Method: Hierarchical Generalized Morphological Component Analysis
• Data driven foreground clustering approach to component separation in multifrequency CMB experiments: A new Planck CMB map
• Scattering Networks on the Sphere for Scalable and Rotationally Equivariant Spherical CNNs
• Deep Needlet: A CNN based full sky component separation method in Needlet space
• Needlet estimation of cross-correlation between CMB lensing maps and LSS
• Thermal Sunyaev-Zeldovich measurements and cosmic infrared background leakage mitigation combining upcoming ground-based telescopes
• The CMB angular power spectrum via component separation: a study on Planck data
• A new approach of estimating the Galactic thermal dust and synchrotron polarized emission template in the microwave bands