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

• DOI: 10.48550/arxiv.2412.13995
• Publication Date: 2024-01-01
• Authors: Rosenberg, Erik; Gratton, Steven; Challinor, Anthony
• Keywords: Cosmology and Nongalactic Astrophysics (astro-ph.CO); FOS: Physical sciences; Astrophysics - Instrumentation and Methods for Astrophysics; Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics - Cosmology and Nongalactic Astrophysics

15 pages, 8 figures<br/>Motivated by observed discrepancies between 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.<br/>