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arXiv · 2505.02827

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

J. A. Zebrowski·C. L. Reichardt·A. J. Anderson·B. Ansarinejad·M. Archipley·L. Balkenhol·P. Barry·K. Benabed·A. N. Bender·B. A. Benson·F. Bianchini·L. E. Bleem·F. R. Bouchet·L. Bryant·E. Camphuis·J. E. Carlstrom·C. L. Chang·P. Chaubal·P. M. Chichura·A. Chokshi·T. -L. Chou·A. Coerver·T. M. Crawford·C. Daley·T. de Haan·K. R. Dibert·M. A. Dobbs·M. Doohan·A. Doussot·D. Dutcher·W. Everett·C. Feng·K. R. Ferguson·K. Fichman·A. Foster·S. Galli·A. E. Gambrel·R. W. Gardner·F. Ge·N. Goeckner-Wald·R. Gualtieri·F. Guidi·S. Guns·N. W. Halverson·E. Hivon·G. P. Holder·W. L. Holzapfel·J. C. Hood·A. Hryciuk·N. Huang·F. Kéruzoré·A. R. Khalife·L. Knox·M. Korman·K. Kornoelje·C. -L. Kuo·K. Levy·Y. Li·A. E. Lowitz·C. Lu·G. P. Lynch·A. Maniyar·E. S. Martsen·F. Menanteau·M. Millea·J. Montgomery·Y. Nakato·T. Natoli·G. I. Noble·Y. Omori·A. Ouellette·Z. Pan·P. Paschos·K. A. Phadke·A. W. Pollak·K. Prabhu·W. Quan·S. Raghunathan·M. Rahimi·A. Rahlin·M. Rouble·J. E. Ruhl·A. Simpson·E. Schiappucci·J. A. Sobrin·A. A. Stark·J. Stephen·C. Tandoi·B. Thorne·C. Trendafilova·C. Umilta·J. D. Vieira·A. G. Vieregg·A. Vitrier·Y. Wan·N. Whitehorn·W. L. K. Wu·M. R. Young
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Abstract

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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J. A. Zebrowski, C. L. Reichardt, A. J. Anderson, B. Ansarinejad, M. Archipley, L. Balkenhol, P. Barry, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, L. E. Bleem, F. R. Bouchet, L. Bryant, E. Camphuis, J. E. Carlstrom, C. L. Chang, P. Chaubal, P. M. Chichura, A. Chokshi, T. -L. Chou, A. Coerver, T. M. Crawford, C. Daley, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, A. Doussot, D. Dutcher, W. Everett, C. Feng, K. R. Ferguson, K. Fichman, A. Foster, S. Galli, A. E. Gambrel, R. W. Gardner, F. Ge, N. Goeckner-Wald, R. Gualtieri, F. Guidi, S. Guns, N. W. Halverson, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, A. Hryciuk, N. Huang, F. Kéruzoré, A. R. Khalife, L. Knox, M. Korman, K. Kornoelje, C. -L. Kuo, K. Levy, Y. Li, A. E. Lowitz, C. Lu, G. P. Lynch, A. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, G. I. Noble, Y. Omori, A. Ouellette, Z. Pan, P. Paschos, K. A. Phadke, A. W. Pollak, K. Prabhu, W. Quan, S. Raghunathan, M. Rahimi, A. Rahlin, M. Rouble, J. E. Ruhl, A. Simpson, E. Schiappucci, J. A. Sobrin, A. A. Stark, J. Stephen, C. Tandoi, B. Thorne, C. Trendafilova, C. Umilta, J. D. Vieira, A. G. Vieregg, A. Vitrier, Y. Wan, N. Whitehorn, W. L. K. Wu, M. R. Young. 2025-05-05. Constraints on Inflationary Gravitational Waves with Two Years of SPT-3G Data. https://arxiv.org/abs/2505.02827

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