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arxiv: 2505.02827 · v1 · pith:HXGE2MZKnew · submitted 2025-05-05 · 🌌 astro-ph.CO

Constraints on Inflationary Gravitational Waves with Two Years of SPT-3G Data

classification 🌌 astro-ph.CO
keywords spt-3gdatabicepkeckpowerareanoisesurvey
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We present a measurement of the $B$-mode polarization power spectrum of the cosmic microwave background anisotropies at 32 $\le$ $\ell$ $<$ 502 for three bands centered at 95, 150, and 220 GHz using data from the SPT-3G receiver on the South Pole Telescope. This work uses SPT-3G observations from the 2019 and 2020 winter observing seasons of a $\sim$1500 deg$^2$ patch of sky that directly overlaps with fields observed with the BICEP/Keck family of telescopes, and covers part of the proposed Simons Observatory and CMB-S4 deep fields. Employing new techniques for mitigating polarized atmospheric noise, the SPT-3G data demonstrates a white noise level of 9.3 (6.7) $\mu$K-arcmin at $\ell \sim 500$ for the 95 GHz (150 GHz) data, with a $1/\ell$ noise knee at $\ell$=128 (182). We fit the observed six auto- and cross-frequency $B$-mode power spectra to a model including lensed $\Lambda$CDM $B$-modes and a combination of Galactic and extragalactic foregrounds. This work characterizes foregrounds in the vicinity of the BICEP/Keck survey area, finding foreground power consistent with that reported by the BICEP/Keck collaboration within the same region, and a factor of $\sim$ 3 higher power over the full SPT-3G survey area. Using SPT-3G data over the BICEP/Keck survey area, we place a 95% upper limit on the tensor-to-scalar ratio of $r < 0.25$ and find the statistical uncertainty on $r$ to be $\sigma(r) = 0.067$.

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

    astro-ph.CO 2025-06 accept novelty 6.0

    SPT-3G delivers the most precise CMB EE and TE spectra at high multipoles to date, giving LCDM parameters with H0 = 66.66 ± 0.60 km/s/Mpc from ground-based data alone and reaching Planck-level constraints when combine...