Measurements of the Temperature and E-mode Polarization of the Cosmic Microwave Background from the Full 500-square-degree SPTpol Dataset (2501.06890v1)

Abstract: Using the full four-year SPTpol 500 deg$^2$ dataset in both the 95 GHz and 150 GHz frequency bands, we present measurements of the temperature and $E$-mode polarization of the cosmic microwave background (CMB), as well as the $E$-mode polarization auto-power spectrum ($EE$) and temperature-$E$-mode cross-power spectrum ($TE$) in the angular multipole range $50<\ell<8000$. We find the SPTpol dataset to be self-consistent, passing several internal consistency tests based on maps, frequency bands, bandpowers, and cosmological parameters. The full SPTpol dataset is well-fit by the $\Lambda CDM$ model, for which we find $H_0=70.48\pm2.16$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_m=0.271\pm0.026$, when using only the SPTpol data and a Planck-based prior on the optical depth to reionization. The $\Lambda CDM$ parameter constraints are consistent across the 95 GHz-only, 150 GHz-only, $TE$-only, and $EE$-only data splits. Between the $\ell<1000$ and $\ell>1000$ data splits, the $\Lambda CDM$ parameter constraints are borderline consistent at the $\sim2\sigma$ level. This consistency improves when including a parameter $A_L$, the degree of lensing of the CMB inferred from the smearing of acoustic peaks. When marginalized over $A_L$, the $\Lambda CDM$ parameter constraints from SPTpol are consistent with those from Planck. The power spectra presented here are the most sensitive measurements of the lensed CMB damping tail to date for roughly $\ell > 1700$ in $TE$ and $\ell > 2000$ in $EE$.

• The paper presents sensitive measurements of the lensed CMB damping tail, extending angular multipole limits in the TE and EE spectra.
• The study yields robust ΛCDM parameters (H0 = 70.48 ± 2.16 km/s/Mpc, Ωm = 0.271 ± 0.026) while confirming internal data consistency across frequencies.
• The research addresses low-level cosmic tensions and establishes a benchmark for future high-resolution CMB studies with upcoming experiments.

Measurements of the Cosmic Microwave Background from the SPTpol Dataset

The paper "Measurements of the Temperature and E-mode Polarization of the Cosmic Microwave Background from the Full 500-square-degree SPTpol Dataset" presents a comprehensive analysis of the Cosmic Microwave Background (CMB) using data from the South Pole Telescope's polarization-sensitive camera (SPTpol). The paper utilizes an extensive dataset spanning four years, covering 500 square degrees in both the 95 GHz and 150 GHz frequency bands. This paper focuses on deriving measurements of the temperature and E-mode polarization, alongside presenting the E-mode polarization auto-power spectrum (EE) and the temperature-E-mode cross-power spectrum (TE) in the angular multipole range from 50 to 8000.

Key Findings

This work contributes to the field by providing some of the most sensitive measurements of the lensed CMB damping tail to date, particularly in the angular multipole ranges beyond $\ell > 1700$ in TE and $\ell > 2000$ in EE. The results bolster the $\Lambda CDM$ model, a cornerstone theory in cosmology describing the universe's large-scale structure. The analysis yields $H_0 = 70.48 \pm 2.16$ km/s/Mpc and $\Omega_m = 0.271 \pm 0.026$, specifically from the SPTpol data supplemented with a Planck prior on the optical depth to reionization.

SPTpol’s dataset is shown to be internally consistent through various tests on maps, frequency bands, and cosmological parameters. This internal consistency is an important validation check, especially considering the $\Lambda CDM$ model parameters are consistent across frequency splits and power spectra, namely the 95 GHz-only, 150 GHz-only, TE-only, and EE-only data.

Implications and Observations

The paper addresses previous tensions observed within CMB data. Notably, while some expected disagreements, such as those between the early and late-time universe observations, have been potentially resolved, there remain low-level disagreements characterized by a $\sim 2\sigma$ difference when splitting data at $\ell < 1000$ and $\ell > 1000$. These distinctions can largely vanish when accounting for a parameter $A_L$ concerning CMB lensing.

The experiment acknowledges a subtle yet consistent preference across their analysis for an $A_L$ value lower than 1, suggesting less lensing than what the Planck data anticipates. This observation remains intriguing as the statistical significance is weak, yet it emphasizes the need for continued exploration of potential systematic biases or new physics explanations.

Future Developments

This work sets a benchmark for future high-sensitivity studies of the CMB, encouraging further investigations with upcoming high-resolution experiments such as SPT-3G, ACT, the Simons Observatory, and CMB-S4. These forthcoming datasets will not only aim to provide a more refined analysis of CMB parameters but may also address lingering questions surrounding cosmic variance and probe deeper into cosmological phenomena like dark energy and inflationary physics. The continued overlap and collaboration with satellite missions will be crucial in cementing these findings and addressing cosmic tensions more robustly.

In summary, the measurement techniques and findings from the SPTpol offer significant contributions to our understanding of the CMB and cosmological parameters, offering clarity to some aspects of the cosmic microwave background while paving the way for future discoveries in cosmology.