Constraints on Ultra-Light Axions from the DESI DR1 Full Shape, Planck and ACT

arXiv:2607.11876 · astro-ph.CO, hep-ph · Submitted 2026-07-13 · Read on arXiv

Francesco Verdiani, Emanuele Castorina, Ennio Salvioni, Emiliano Sefusatti, Matteo Viel

astro-ph.CO, hep-ph

Submitted: 2026-07-13

Comments: 10 pages + appendices and references, 8 figures, 2 tables

Code: https://github.com/cosmodesi/pypower

License: http://creativecommons.org/licenses/by/4.0/

The gist: We present updated bounds on ultra-light axions (ULAs) as a subcomponent of dark matter, derived from the full-shape analysis of the DESI Data Release 1 galaxy power spectra combined with Cosmic

Terminology

Abstract

We present updated bounds on ultra-light axions (ULAs) as a subcomponent of dark matter, derived from the full-shape analysis of the DESI Data Release 1 galaxy power spectra combined with Cosmic Microwave Background (CMB) data from ACT and Planck. We focus on the mass window 10-32, eV at most m a at most 10-24, eV, employing state-of-the-art analysis methods rooted in the Effective Field Theory of Large Scale Structure. For the smallest masses, our joint analysis with DESI improves over CMB-only constraints by more than a factor of 2, establishing the most stringent limits to date. For instance, for m a about 10-29, eV ULAs are constrained to be a fraction as small as 0.3% of the total matter energy density. The DESI Luminous Red Galaxy sample shows a mild preference for an ULA subcomponent with m a about 10-26, eV, mirroring previous hints from BOSS, but this preference vanishes upon combination with CMB data. Probing the largest masses, m a 10-25, eV, in future studies will benefit from extending the data analysis to smaller scales, both for galaxy clustering and CMB lensing, but will also require concurrent improvements in the theoretical modeling.

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