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 $1.020\pm0.060$, 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 $1\sigma$ 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.).
Categories: astro-ph.CO