The Atacama Cosmology Telescope: Large-scale velocity reconstruction with the kinematic Sunyaev-Zel'dovich effect and DESI LRGs

McCarthy, Fiona, Battaglia, Nicholas, Bean, Rachel, Richard Bond, J., Cai, Hongbo, Calabrese, Erminia ORCID: https://orcid.org/0000-0003-0837-0068, Coulton, William R., Devlin, Mark J., Dunkley, Jo, Ferraro, Simone, Gluscevic, Vera, Guan, Yilun, Colin Hill, J., Johnson, Matthew C., Kusiak, Aleksandra, Laguë, Alex, MacCrann, Niall, Madhavacheril, Mathew S., Moodley, Kavilan, Naess, Sigurd, Qu, Frank J., Guachalla, Bernardita Ried, Sehgal, Neelima, Sherwin, Blake D., Sifón, Cristóbal, Smith, Kendrick M., Staggs, Suzanne T., van Engelen, Alexander, Vavagiakis, Eve M. and Wollack, Edward J. 2025. The Atacama Cosmology Telescope: Large-scale velocity reconstruction with the kinematic Sunyaev-Zel'dovich effect and DESI LRGs. Journal of Cosmology and Astroparticle Physics 2025 (05) , 057. 10.1088/1475-7516/2025/05/057

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Abstract

The kinematic Sunyaev-Zel'dovich (kSZ) effect induces a non-zero density-density-temperature bispectrum, which we can use to reconstruct the large-scale velocity field from a combination of cosmic microwave background (CMB) and galaxy density measurements, in a procedure known as “kSZ velocity reconstruction”. This method has been forecast to constrain large-scale modes with future galaxy and CMB surveys, improving their measurement beyond what is possible with the galaxy surveys alone. Such measurements will enable tighter constraints on large-scale signals such as primordial non-Gaussianity, deviations from homogeneity, and modified gravity. In this work, we demonstrate a statistically significant measurement of kSZ velocity reconstruction for the first time, by applying quadratic estimators to the combination of the ACT DR6 CMB+kSZ map and the DESI LRG galaxies (with photometric redshifts) in order to reconstruct the velocity field. We do so using a formalism appropriate for the 2-dimensional projected galaxy fields that we use, which naturally incorporates the curved-sky effects important on the largest scales. We find evidence for the signal by cross-correlating with an external estimate of the velocity field from the spectroscopic BOSS survey and rejecting the null (no-kSZ) hypothesis at 3.8σ. Our work presents a first step towards the use of this observable for cosmological analyses.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/4.0/, Type: cc-by
Publisher:	IOP Publishing
Date of First Compliant Deposit:	23 May 2025
Date of Acceptance:	31 March 2025
Last Modified:	23 May 2025 11:44
URI:	https://orca.cardiff.ac.uk/id/eprint/178466

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