Charles L. Bennett

Unexpected features have been observed in the cosmic microwave background (CMB) temperature on large scales. We revisit these CMB anomalies using new foreground-cleaned CMB temperature maps derived in a companion paper from WMAP and Planck data, which are tailored to low-resolution analysis and require only minimal masking of 1% of the sky. These maps allow us to assess the impact of foreground-cleaning methods and the choice of sky cut on the significance of five commonly studied CMB anomalies. We find a notable impact of the choice of galactic mask on the significance of two anomalies: the significance of the low real-space correlation function and of the local-variance asymmetry reduces from ∼3 σ for the Planck common mask with 26% masked fraction to ∼2 σ for the 1% mask. We find good agreement between the two sky cuts for the low northern variance, ∼3 σ , and the parity asymmetry, ∼2 σ . For the quadrupole-octopole alignment, we find good agreement between the 1% mask result and the full-sky results in the literature, ∼3 σ . Thus, using a larger fraction of the sky enabled by improved foreground cleaning reduces the significance of two commonly studied CMB anomalies. Overall, for an alternative physical model to be convincingly favored over Λ cold dark matter (CDM) with statistically isotropic Gaussian fluctuations, it would need to explain multiple CMB anomalies, or better describe some other type of measurement in addition to a CMB anomaly.

We present a cosmic microwave background (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 the first paper of this series. We recover essentially the full-sky CMB information at multipoles ℓ < 30 with only 1% of pixels near the Galactic plane masked and with no inpainting. Notable features continue to appear: (a) a low quadrupole power compared to the best-fit Planck 2018 ΛCDM spectrum at 2.2 σ , (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 1.2 σ and 0.6 σ , 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 H ₀ = 67.35 ± 0.54 km s ⁻¹ Mpc ⁻¹ in a joint ΛCDM fit.

Studies of cosmic microwave background (CMB) are often limited by foreground contamination. Foreground cleaning is performed in either harmonic or pixel space after data cuts have excluded sky areas of strong contamination. We present a nearly full-sky CMB temperature map with only 1% of pixels masked. To derive this map, we make use of six full-sky template maps at foreground-dominated frequencies from different experiments smoothed to 1° and rely on the combination of these weighted maps to trace the morphology of foreground contamination. We do not impose any spectral index constraints but only fit for template amplitudes at each target frequency. We clean Wilkinson Microwave Anisotropy Probe and Planck maps at a set of target frequencies and conduct quality tests at the level of the maps, pixel histograms, and power spectra to select four CMB maps that are cleaned with negligible foreground contamination and only 1% masked pixels and no inpainting. We recommend use of these cleaned CMB maps for low-multipole ( ℓ < 30) studies.

Infrared-blocking, aerogel-based scattering filters have a broad range of potential applications in astrophysics and planetary science instruments in the far-infrared, sub-millimeter, and microwave regimes. This paper demonstrates the ability of conductively loaded, polyimide aerogel filters to meet the mechanical and science instrument requirements for several experiments, including the Cosmology Large Angular Scale Surveyor, the Experiment for Cryogenic Large-Aperture Intensity Mapping, and the Sub-millimeter Solar Observation Lunar Volatiles Experiment. Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties. Measurement of total hemispherical reflectance and transmittance as well as cryogenic tests of the aerogel filters in a full receiver context allows estimates of the integrated infrared emissivity of the filters. Knowledge of the emissivity will help instrument designers incorporate the filters into future experiments in planetary science, astrophysics, and cosmology.

We present measurements of large-scale cosmic microwave background E-mode polarization from the Cosmology Large Angular Scale Surveyor 90 GHz data. Using 115 det-yr of observations collected through 2024 with a variable-delay polarization modulator, we achieved a polarization sensitivity of 82 μ K arcmin , comparable to Planck at similar frequencies (100 and 143 GHz ). The analysis demonstrates effective mitigation of systematic errors and addresses challenges to large-angular-scale power recovery posed by time-domain filtering in maximum-likelihood map-making. A novel implementation of the pixel-space transfer matrix is introduced, which enables efficient filtering simulations and bias correction in the power spectrum using the quadratic cross-spectrum estimator. Overall, we achieved an unbiased time-domain filtering correction to recover the largest angular scale polarization, with the only power deficit, arising from map-making nonlinearity, being characterized as τ = 0.05 3 − 0.019 + 0.018 , marking the first ground-based attempt at such a measurement. At intermediate angular scales (ℓ > 30), our results, both independently and in cross-correlation with Planck, remain fully consistent with Planck’s measurements.

We present the in-lab and on-sky performance for the upgraded 90 GHz focal plane of the Cosmology Large Angular Scale Surveyor, which had four of its seven detector wafers updated during the austral winter of 2022. The update aimed to improve the transition-edge-sensor (TES) stability and bias range and to realize the high optical efficiency of the sensor design. Modifications included revised circuit terminations, electrical contact between the TES superconductor and the normal metal providing the bulk of the bolometer heat capacity, and additional filtering on the TES bias lines. The upgrade was successful: 94% of detectors are stable down to 15% of the normal resistance, providing a wide overlapping range of bias voltages for all TESs on a wafer. The median telescope efficiency improved from 0.4 2 − 0.22 + 0.15 to 0.6 0 − 0.32 + 0.10 (68% quantiles). For the four upgraded wafers alone, median telescope efficiency increased to 0.6 5 − 0.06 + 0.06 . Given our efficiency estimate for the receiver optics, this telescope efficiency implies a detector efficiency exceeding 0.90. The overall noise-equivalent temperature of the 90 GHz focal plane improved from 19 μ K s to 9.7 μ K s .