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The Atacama Cosmology Telescope: Cosmology from cross-correlations of unWISE galaxies and ACT DR6 CMB lensing

Farren, Gerrit S., Krolewski, Alex, MacCrann, Niall, Ferraro, Simone, Abril-Cabezas, Irene, An, Rui, Atkins, Zachary, Battaglia, Nicholas, Bond, J. Richard, Calabrese, Erminia ORCID:, Choi, Steve K., Darwish, Omar, Devlin, Mark J., Duivenvoorden, Adriaan J., Dunkley, Jo, Hill, J. Colin, Hilton, Matt, Huffenberger, Kevin M., Kim, Joshua, Louis, Thibaut, Madhavacheril, Mathew S., A. Marques, Gabriela, McMahon, Jeff, Moodley, Kavilan, Page, Lyman A., Partridge, Bruce, Qu, Frank J., Schaan, Emmanuel, Sehgal, Neelima, Sherwin, Blake D., Sifón, Cristóbal, Staggs, Suzanne T., Van Engelen, Alexander, Vargas, Cristian, Wenzl, Lukas, White, Martin and Wollack, Edward J. 2024. The Atacama Cosmology Telescope: Cosmology from cross-correlations of unWISE galaxies and ACT DR6 CMB lensing. The Astrophysical Journal 966 (2) , 157. 10.3847/1538-4357/ad31a5

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We present tomographic measurements of structure growth using cross-correlations of Atacama Cosmology Telescope (ACT) DR6 and Planck cosmic microwave background (CMB) lensing maps with the unWISE Blue and Green galaxy samples, which span the redshift ranges 0.2 ≲ z ≲ 1.1 and 0.3 ≲ z ≲ 1.8, respectively. We improve on prior unWISE cross-correlations not just by making use of the new, high-precision ACT DR6 lensing maps, but also by including additional spectroscopic data for redshift calibration and by analyzing our measurements with a more flexible theoretical model. We determine the amplitude of matter fluctuations at low redshifts (z ≃ 0.2–1.6), finding S8≡σ8(Ωm/0.3)0.5=0.813±0.021 using the ACT cross-correlation alone and S 8 = 0.810 ± 0.015 with a combination of Planck and ACT cross-correlations; these measurements are fully consistent with the predictions from primary CMB measurements assuming standard structure growth. The addition of baryon acoustic oscillation data breaks the degeneracy between σ 8 and Ω m , allowing us to measure σ 8 = 0.813 ± 0.020 from the cross-correlation of unWISE with ACT and σ 8 = 0.813 ± 0.015 from the combination of cross-correlations with ACT and Planck. These results also agree with the expectations from primary CMB extrapolations in ΛCDM cosmology; the consistency of σ 8 derived from our two redshift samples at z ∼ 0.6 and 1.1 provides a further check of our cosmological model. Our results suggest that structure formation on linear scales is well described by ΛCDM even down to low redshifts z ≲ 1.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Advanced Research Computing @ Cardiff (ARCCA)
Physics and Astronomy
Additional Information: License information from Publisher: LICENSE 1: URL:, Type: cc-by
Publisher: American Astronomical Society
ISSN: 0004-637X
Date of First Compliant Deposit: 3 May 2024
Date of Acceptance: 6 March 2024
Last Modified: 11 Jun 2024 12:31

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