SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field

Kavli Affiliate: Chao-Lin Kuo

| First 5 Authors: E. Camphuis, W. Quan, L. Balkenhol, A. R. Khalife, F. Ge

| Summary:

We present measurements of the temperature and E-mode polarization angular
power spectra of the cosmic microwave background (CMB) from observations of 4%
of the sky with SPT-3G, the current camera on the South Pole Telescope (SPT).
The maps used in this analysis are the deepest used in a CMB TT/TE/EE analysis
to date. The maps and resulting power spectra have been validated through blind
and unblind tests. The measurements of the lensed EE and TE spectra are the
most precise to date at l=1800-4000 and l=2200-4000, respectively. Combining
our TT/TE/EE spectra with previously published SPT-3G CMB lensing results, we
find parameters for the standard LCDM model consistent with Planck and ACT-DR6
with comparable constraining power. We report a Hubble constant of
$H_0=66.66pm0.60$ km/s/Mpc from SPT-3G alone, 6.2 sigma away from local
measurements from SH0ES. For the first time, combined ground-based (SPT+ACT)
CMB primary and lensing data have reached Planck’s constraining power on some
parameters, a milestone for CMB cosmology. The combination of these three CMB
experiments yields the tightest CMB constraints to date, with
$H_0=67.24pm0.35$ km/s/Mpc, and the amplitude of clustering
$sigma_8=0.8137pm0.0038$. CMB data alone show no evidence for physics beyond
LCDM; however, we observe a 2.8 sigma difference in LCDM between CMB and baryon
acoustic oscillation (BAO) results from DESI-DR2, which is relaxed in extended
models. The combination of CMB and BAO yields 2-3 sigma shifts from LCDM in the
curvature of the universe, the amplitude of CMB lensing, or the dark energy
equation of state. It also drives mild preferences for models that address the
Hubble tension through modified recombination or variations in the electron
mass in a non-flat universe. This work highlights the growing power of
ground-based CMB experiments and lays a foundation for further cosmological
analyses with SPT-3G.

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