Sound-horizon-agnostic Inference of the Hubble Constant and Neutrino Masses from Baryon Acoustic Oscillations, Cosmic Microwave Background Lensing, and Galaxy Weak Lensing and Clustering

Abstract We present a sound-horizon-agnostic determination of the Hubble constant, H 0 , by combining DESI Data Release 2 baryon acoustic oscillations (BAO) data with the latest cosmic microwave background (CMB) lensing measurements from Planck, the Atacama Cosmology Telescope, and SPT-3G, the angular size of the CMB acoustic scale, Dark Energy Survey Year 3 (3 × 2 pt) galaxy weak lensing and clustering correlations, and the Pantheon+ supernova sample. In this analysis, The sound horizon at the drag epoch, r d , is treated as a free parameter. By combining uncalibrated comoving distances from BAO and supernovae with constraints on the matter density Ω m h 2 from CMB and galaxy lensing and clustering, we break the r d – H 0 degeneracy and obtain H 0 = 70.0 ± 1.7 km s −1 Mpc −1 when the sum of the neutrino masses is fixed at Σ m ν = 0.06 eV. With an informative prior on the amplitude of primordial fluctuations, A s , we find H 0 = 70.03 ± 0.9 km s −1 Mpc −1 . Allowing Σ m ν to vary, we find that the neutrino mass is weakly constrained and strongly prior dependent. Consequently, the inferred H 0 is sensitive to the choice of the Σ m ν prior, with a uniform prior biasing results toward larger neutrino masses and higher H 0 , while a logarithmic prior reduces this bias significantly. Forecasts for the completed DESI BAO program, combined with Simons Observatory–like CMB lensing, next-generation 3 × 2 pt data, and expanded supernova samples predict σ ( H 0 ) ≃ 0.67 km s −1 Mpc −1 with fixed Σ m ν , and σ ( H 0 ) ≃ 1.1 km s −1 Mpc −1 with Σ m ν < 0.133 eV (<0.263 eV) at 68% (95%) confidence limit when Σ m ν is varied.