2025/09/03 by Nofi, Hayley C., Addison, Graeme E., Bennett, Charles L. +2 · 2 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2509.03719
We present a CMB temperature power spectrum measurement at large angular scales from WMAP and Planck maps that were cleaned of foregrounds using a template-based approach described in a companion paper. We recover essentially the full-sky CMB information at multipoles ℓ<30 with only 1% of pixels near the Galactic plane masked and no inpainting. Notable features continue to appear: (a) a low quadrupole power compared to the best-fit Planck 2018 ΛCDM spectrum at 2.2σ, (b) a dip in the range 20 ≤ ℓ ≤ 27, and (c) an overall ℓ<30 power level low of the ΛCDM prediction derived from higher multipole moments. Given the different methodology from previous analyses and the nearly full-sky solution presented here, these features do not plausibly arise from foreground contamination, systematic errors, masking, or mode-mixing. Our overall ℓ<30 amplitude constraint is consistent with published WMAP (77% sky fraction) and Planck (86%) results at 1.2σ and 0.6σ, respectively, accounting for the improvement in statistical precision. We present a new ℓ<30 likelihood for use with the Cobaya package. Parameter constraints from joint fits with the higher-multipole Planck data are consistent with the published Planck results, for example we find H0=67.35±0.54 km s-1 Mpc-1 in a joint ΛCDM fit.