SPT-3G D1: Quadratic-Estimator CMB Lensing Reconstruction and Cosmology

arXiv:2608.31136 · astro-ph.CO · Submitted 2026-08-31 · Read on arXiv

astro-ph.CO

Submitted: 2026-08-31

Updated: 2026-08-31

Comments: 75 pages, 37 figures

Code: https://github.com/ACTCollaboration/DR6-ACT-lite

License: http://creativecommons.org/licenses/by/4.0/

The gist: We present a map of the cosmic microwave background (CMB) lensing potential reconstructed from observations taken during the 2019 and 2020 seasons with the third-generation camera on the South Pole

Terminology

Abstract

We present a map of the cosmic microwave background (CMB) lensing potential reconstructed from observations taken during the 2019 and 2020 seasons with the third-generation camera on the South Pole Telescope (SPT), covering the 1500, deg squared SPT-3G Main field, referred to as the SPT-3G D1 dataset. From the multi-frequency temperature and polarization data, we reconstruct the CMB lensing field using a quadratic estimator that jointly accounts for the T, E, and B fields and their covariance. The resulting lensing map is dominated by polarization information for L 600 and provides the highest signal-to-noise measurement per mode reported to date. With nuisance parameters fixed to their best-fit values, we measure a lensing amplitude consistent with unity at 2% precision relative to the Λ CDM model that best fits the combined Planck, ACT DR6, and SPT-3G D1 TT/TE/EE likelihoods (CMB SPA). We further measure the structure-growth parameter σ 8Ω m 0.25 to be 0.6046 plus or minus0.0096 from the SPT-3G D1 lensing spectrum alone and 0.6020 plus or minus0.0084 when combined with ACT DR6 and Planck PR4 CMB lensing. By further combining this with CMB SPA and the latest DESI DR2 BAO data, we obtain sum m ν < 0.072, eV (95% C.L.) when allowing the neutrino mass to vary within Λ CDM. Compared with previous work, the better agreement of our measurement with DESI DR2 BAO yields both this relaxed upper bound and reduced (2σ) preferences for nonzero spatial curvature and for deviations of (w 0,w a) from the Λ CDM expectation. When we combine CMB lensing with the DES Y3 3 times 2pt analysis, we obtain S 8=0.811 plus or minus0.011, corresponding to a 1.4% constraint on the late-time clustering amplitude. This precision is competitive with that obtained from the primary CMB within Λ CDM.

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