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  • Open Access

Filtering in CMB data analysis with application to ACT DR4 and Planck observations

Erik Rosenberg1,2,3,*, Steven Gratton4,2,3, and Anthony Challinor2,3,4

  • *Contact author: erik.rosenberg@manchester.ac.uk
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Phys. Rev. D 112, 023534 – Published 18 July, 2025

DOI: https://doi.org/10.1103/rvhm-fsdc

Abstract

Motivated by observed discrepancies between the Atacama Cosmology Telescope Data Release 4 (ACT DR4) and Planck 2018 cosmic microwave background (CMB) anisotropy power spectra, particularly in the cross-correlation of temperature and E-mode polarization, we investigate challenges that may be encountered in the comparison of satellite and ground-based CMB data. In particular, we focus on the effects of Fourier-space filtering and masking involving bright point sources. We show that the filtering operation generates bright cross-shaped artifacts in the map, which stretch far outside typical point-source masks. If not corrected, these artifacts can add bias or additional variance to cross-spectra, skewing results. However we find that the effect of this systematic is not large enough to explain the ACT-Planck differences presented with ACT DR4.

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Phys. Rev. D 112, 023534– Published 18 July, 2025
  • Received 31 December 2024
  • Accepted 19 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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