English

SPT-3G D1: Foreground-Robust Lensing Templates for Primordial Gravitational Wave Searches

Cosmology and Nongalactic Astrophysics 2026-08-06 v1
Authors: Y. Nakato , W. L. K. Wu , Y. Omori , E. Anderes , A. J. Anderson , B. Ansarinejad , M. Archipley , L. Balkenhol , D. R. Barron , P. S. Barry , K. Benabed , A. N. Bender , B. A. Benson , F. Bianchini , L. E. Bleem , S. Bocquet , F. R. Bouchet , E. Camphuis , M. G. Campitiello , J. E. Carlstrom , J. Carron , C. L. Chang , 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 , D. Dutcher , C. Feng , K. R. Ferguson , N. C. Ferree , K. Fichman , A. Foster , S. Galli , A. E. Gambrel , A. K. Gao , F. Ge , F. Guidi , S. Guns , N. W. Halverson , E. Hivon , G. P. Holder , W. L. Holzapfel , J. C. Hood , A. Hryciuk , N. Huang , T. Jhaveri , F. Kéruzoré , A. R. Khalife , L. Knox , K. Kornoelje , C. -L. Kuo , K. Levy , Y. Li , A. E. Lowitz , C. Lu , G. P. Lynch , T. J. Maccarone , A. S. Maniyar , E. S. Martsen , F. Menanteau , M. Millea , J. Montgomery , T. Natoli , A. Ouellette , Z. Pan , P. Paschos , K. A. Phadke , K. Prabhu , W. Quan , S. Raghunathan , M. Rahimi , A. Rahlin , C. L. Reichardt , M. Rouble , J. E. Ruhl , A. C. Silva Oliveira , A. Simpson , J. A. Sobrin , A. A. Stark , J. Stephen , C. Tandoi , C. Trendafilova , J. D. Vieira , A. G. Vieregg , A. Vitrier , Y. Wan , N. Whitehorn , M. R. Young , J. A. Zebrowski
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Abstract

Gravitational lensing of the cosmic microwave background (CMB) generates B-mode polarization that acts as a source of contamination to searches for B modes generated by primordial gravitational waves (PGWs). The strongest constraint on PGW B modes is already significantly limited by lensing B modes, as shown in the most recent BICEP result. In this work, we present CMB lensing B-mode templates constructed using SPT-3G and Planck data, which characterize the lensing B modes and can be used to improve PGW B-mode searches. We use SPT-3G data from the 2019 and 2020 observing seasons for the E modes and the CMB-reconstructed lensing potential, and a cosmic infrared background (CIB) map from Planck as an external lensing tracer. To test for extragalactic foreground biases in the lensing template, we consider CMB lensing reconstruction variants with different levels of foreground immunity: the standard and profile-hardened global minimum variance (GMV) quadratic estimators, and a polarization-only quadratic estimator. We validate the template construction using Gaussian simulations and Agora simulations with realistic non-Gaussian foregrounds. From simulations, we find that foreground-induced biases are strongly suppressed for the template constructed with the profile-hardened GMV + CIB tracer, with residual bias below 10% of the statistical uncertainty on the template power spectrum. Data difference tests on this template similarly show no evidence for significant foreground contamination. This foreground-immune lensing template achieves delensed residual BB power of Alensres≃0.48A_{\rm lens}^{\rm res} \simeq 0.48 averaged over 20≤ℓ≤20020 \leq \ell \leq 200, the highest delensing efficiency lensing template to date. These results demonstrate and validate a method to construct foreground-robust lensing templates which will be used in upcoming delensed PGW B-mode analyses of BICEP data.

Keywords

CMB lensing B-mode polarization primordial gravitational waves SPT-3G foreground robustness delensing lensing templates

Cite

@article{arxiv.2608.06343,
  title  = {SPT-3G D1: Foreground-Robust Lensing Templates for Primordial Gravitational Wave Searches},
  author = {Y. Nakato and W. L. K. Wu and Y. Omori and E. Anderes and A. J. Anderson and B. Ansarinejad and M. Archipley and L. Balkenhol and D. R. Barron and P. S. Barry and K. Benabed and A. N. Bender and B. A. Benson and F. Bianchini and L. E. Bleem and S. Bocquet and F. R. Bouchet and E. Camphuis and M. G. Campitiello and J. E. Carlstrom and J. Carron and C. L. Chang and P. M. Chichura and A. Chokshi and T. -L. Chou and A. Coerver and T. M. Crawford and C. Daley and T. de Haan and K. R. Dibert and M. A. Dobbs and M. Doohan and D. Dutcher and C. Feng and K. R. Ferguson and N. C. Ferree and K. Fichman and A. Foster and S. Galli and A. E. Gambrel and A. K. Gao and F. Ge and F. Guidi and S. Guns and N. W. Halverson and E. Hivon and G. P. Holder and W. L. Holzapfel and J. C. Hood and A. Hryciuk and N. Huang and T. Jhaveri and F. Kéruzoré and A. R. Khalife and L. Knox and K. Kornoelje and C. -L. Kuo and K. Levy and Y. Li and A. E. Lowitz and C. Lu and G. P. Lynch and T. J. Maccarone and A. S. Maniyar and E. S. Martsen and F. Menanteau and M. Millea and J. Montgomery and T. Natoli and A. Ouellette and Z. Pan and P. Paschos and K. A. Phadke and K. Prabhu and W. Quan and S. Raghunathan and M. Rahimi and A. Rahlin and C. L. Reichardt and M. Rouble and J. E. Ruhl and A. C. Silva Oliveira and A. Simpson and J. A. Sobrin and A. A. Stark and J. Stephen and C. Tandoi and C. Trendafilova and J. D. Vieira and A. G. Vieregg and A. Vitrier and Y. Wan and N. Whitehorn and M. R. Young and J. A. Zebrowski},
  journal= {arXiv preprint arXiv:2608.06343},
  year   = {2026}
}