Measurements of the Temperature and E-Mode Polarization of the CMB from 500 Square Degrees of SPTpol Data (1707.09353v3)

Abstract: We present measurements of the $E$-mode polarization angular auto-power spectrum ($EE$) and temperature-$E$-mode cross-power spectrum ($TE$) of the cosmic microwave background (CMB) using 150 GHz data from three seasons of SPTpol observations. We report the power spectra over the spherical harmonic multipole range $50 < \ell \leq 8000$, and detect nine acoustic peaks in the $EE$ spectrum with high signal-to-noise ratio. These measurements are the most sensitive to date of the $EE$ and $TE$ power spectra at $\ell > 1050$ and $\ell > 1475$, respectively. The observations cover 500 deg$^2$, a fivefold increase in area compared to previous SPTpol analyses, which increases our sensitivity to the photon diffusion damping tail of the CMB power spectra enabling tighter constraints on \LCDM model extensions. After masking all sources with unpolarized flux $>50$ mJy we place a 95% confidence upper limit on residual polarized point-source power of $D_\ell = \ell(\ell+1)C_\ell/2\pi <0.107\,\mu{\rm K}^2$ at $\ell=3000$, suggesting that the $EE$ damping tail dominates foregrounds to at least $\ell = 4050$ with modest source masking. We find that the SPTpol dataset is in mild tension with the $\Lambda CDM$ model ($2.1\,\sigma$), and different data splits prefer parameter values that differ at the $\sim 1\,\sigma$ level. When fitting SPTpol data at $\ell < 1000$ we find cosmological parameter constraints consistent with those for $Planck$ temperature. Including SPTpol data at $\ell > 1000$ results in a preference for a higher value of the expansion rate ($H_0 = 71.3 \pm 2.1\,\mbox{km}\,s^{-1}\mbox{Mpc}^{-1}$ ) and a lower value for present-day density fluctuations ($\sigma_8 = 0.77 \pm 0.02$).

Measurements of CMB Temperature and E-mode Polarization with SPTpol

This paper presents a comprehensive analysis of the cosmic microwave background (CMB) E-mode polarization angular auto-power spectrum ($EE$) and temperature-E-mode cross-power spectrum ($TE$) using data from the South Pole Telescope Polarimeter (SPTpol). The team capitalized on observations at 150 GHz over 500 square degrees, collected during three seasons. The enhanced sky coverage from previous SPTpol analyses offers superior sensitivity to the photon diffusion damping tail of the CMB.

Key Results and Observations

1. Extended Multipole Range:
   • Power spectra reported span $50 < \ell \leq 8000$.
   • Detected nine acoustic peaks in the $EE$ spectrum with significant signal-to-noise ratios, demonstrating the dataset's precision.
   • The strongest sensitivity in $EE$ and $TE$ measurements surpasses previous records at $\ell > 1050$ and $\ell > 1475$, respectively.
2. Foreground and Noise Considerations:
   • Masking of sources revealed low residual polarized point-source power at $\ell = 3000$, establishing that the $EE$ spectrum predominantly influences foregrounds up to $\ell = 4050$.
   • The dataset exhibits mild tension with the standard $$cosmological model, with discrepancies potentially illuminating new avenues for understanding cosmological phenomena.</li> </ul></li> <li><strong>Parameter Constraints and Future Implications:</strong> <ul> <li>Multipole fitting below$$\ell 1000$$results in consistent cosmological parameter constraints with Planck temperature data.</li> <li>High-$$\ell$$data suggest higher expansion rates and lower present-day density fluctuations, with$$H_{0 = 71.3 \pm 2.1\ km/s/Mpc$and$\sigma_8 = 0.77 \pm 0.02$$.</li> </ul></li> </ol> <h3 class='paper-heading' id='theoretical-and-practical-implications'>Theoretical and Practical Implications</h3> <p>These measurements are critical for refining models of cosmic structure formation and the dynamic evolution of the universe. The findings contribute to the discourse on cosmic variance and the damping tail sensitivity that tests the consistency of the$$ paradigm. A thorough investigation offers intriguing insights that might affect cosmological constants, fostering potential revisions in theoretical physics models, such as those dealing with dark matter and energy or other alternative cosmologies.

     Compared with experiments like Planck and predecessors, this data provides crucial cross-validation opportunities and heightens the prospects for more accurate, larger-scale predictions concerning universe expansion dynamics. Moreover, it sets the stage for further CMB experiments, like SPT-3G and others aligned with CMB-S4 initiatives, enhancing perspective toward a deeper understanding of the early universe's properties.

     Directions for Future Research

     This paper paves the way for more refined investigations into the CMB across larger expanses and finer resolutions, relying on the evolving capabilities of ground-based and satellite mechanisms. Considering the dimensions explored in this analysis, future methodologies should aim toward delving deeper into cross-spectra comparisons with multiple datasets. Addressing potential systematics and calibrations could uncover more stringent cosmological constraints and rectify any existing tensions among datasets.

     Overall, this paper marks a substantial advancement in CMB polarization studies, driving the narrative for cosmological measurements towards broader horizons and improved precision.