A Measurement of Gravitational Lensing of the Cosmic Microwave Background Using SPT-3G 2018 Data

Kavli Affiliate: Chao-Lin Kuo

| First 5 Authors: Z. Pan, F. Bianchini, W. L. K. Wu, P. A. R. Ade, Z. Ahmed

| Summary:

We present a measurement of gravitational lensing over 1500 deg$^2$ of the
Southern sky using SPT-3G temperature data at 95 and 150 GHz taken in 2018. The
lensing amplitude relative to a fiducial Planck 2018 $Lambda$CDM cosmology is
found to be $1.020pm0.060$, excluding instrumental and astrophysical
systematic uncertainties. We conduct extensive systematic and null tests to
check the robustness of the lensing measurements, and report a minimum-variance
combined lensing power spectrum over angular multipoles of $50<L<2000$, which
we use to constrain cosmological models. When analyzed alone and jointly with
primary cosmic microwave background (CMB) spectra within the $Lambda$CDM
model, our lensing amplitude measurements are consistent with measurements from
SPT-SZ, SPTpol, ACT, and Planck. Incorporating loose priors on the baryon
density and other parameters including uncertainties on a foreground bias
template, we obtain a $1sigma$ constraint on $sigma_8 Omega_{rm
m}^{0.25}=0.595 pm 0.026$ using the SPT-3G 2018 lensing data alone, where
$sigma_8$ is a common measure of the amplitude of structure today and
$Omega_{rm m}$ is the matter density parameter. Combining SPT-3G 2018 lensing
measurements with baryon acoustic oscillation (BAO) data, we derive parameter
constraints of $sigma_8 = 0.810 pm 0.033$, $S_8 equiv sigma_8(Omega_{rm
m}/0.3)^{0.5}= 0.836 pm 0.039$, and Hubble constant $H_0 =68.8^{+1.3}_{-1.6}$
km s$^{-1}$ Mpc$^{-1}$. Using CMB anisotropy and lensing measurements from
SPT-3G only, we provide independent constraints on the spatial curvature of
$Omega_{K} = 0.014^{+0.023}_{-0.026}$ (95% C.L.) and the dark energy density
of $Omega_Lambda = 0.722^{+0.031}_{-0.026}$ (68% C.L.). When combining SPT-3G
lensing data with SPT-3G CMB anisotropy and BAO data, we find an upper limit on
the sum of the neutrino masses of $sum m_{nu}< 0.30$ eV (95% C.L.).

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