Atacama Cosmology Telescope: B -mode delensing with DR6 data and external tracers of large-scale structure

Hertig, Emilie, Baleato Lizancos, Antón, Qu, Frank J., Bond, J. Richard, Calabrese, Erminia ORCID: https://orcid.org/0000-0003-0837-0068, Challinor, Anthony, Devlin, Mark J., Dunkley, Jo, Louis, Thibaut, Madhavacheril, Mathew S., Namikawa, Toshiya, Page, Lyman A., Sehgal, Neelima, Sherwin, Blake, Sifón, Cristóbal, Staggs, Suzanne T. and Wollack, Edward J. 2026. Atacama Cosmology Telescope: B -mode delensing with DR6 data and external tracers of large-scale structure. Physical Review D (particles, fields, gravitation, and cosmology) 113 (12) , 123530. 10.1103/ztry-pnlx

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Abstract

Large-scale B -mode polarization of the cosmic microwave background (CMB) is a prime target for current and future experiments in search of primordial gravitational waves. With increasingly sensitive instruments being deployed, secondary B -modes induced by the weak gravitational lensing of CMB photons are becoming an important limitation and need to be removed, a process known as delensing. In this work, we combine internally reconstructed CMB lensing maps from the Atacama Cosmology Telescope (ACT) data release 6 (DR6) with galaxy samples from unWISE and a map of the cosmic infrared background (CIB) fluctuations from Planck to produce a well-correlated tracer of the CMB lensing field. Our coadded tracer, shown to be 55%–85% correlated with the true lensing convergence at multipoles L ≤ 2000 , is then convolved with ACT DR6 E -mode polarization to yield a template of the lensing B -modes. We assess its performance on a wide range of scales by using it to delens ACT DR6 and Planck B -modes over 23% of the sky, removing around 39% of the lensing power at 100 ≤ l ≤ 1500 and 47% at 30 ≤ l ≤ 300 , respectively. Our template achieves the highest delensing efficiency to date and will be useful for the analysis of early polarization maps from the Simons Observatory. We finally outline prospects for further improvements by including additional large-scale structure tracers from upcoming cosmological surveys.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2026-06-15
Publisher:	American Physical Society
ISSN:	2470-0010
Date of First Compliant Deposit:	2 July 2026
Date of Acceptance:	17 April 2026
Last Modified:	02 Jul 2026 12:45
URI:	https://orca.cardiff.ac.uk/id/eprint/187881

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