The Local Distance Network: a community consensus report on the measurement of the Hubble constant at 1% precision
Authors
H0DN Collaboration
Stefano Casertano
Gagandeep Anand
Richard I. Anderson
Rachael Beaton
Anupam Bhardwaj
John P. Blakeslee
Paula Boubel
Louise Breuval
Dillon Brout
Michele Cantiello
Mauricio Cruz Reyes
Geza Csörnyei
Thomas de Jaeger
Suhail Dhawan
Eleonora Di Valentino
Lluís Galbany
Héctor Gil-Marín
Dariusz Graczyk
Caroline Huang
Joseph B. Jensen
Pierre Kervella
Bruno Leibundgut
Bastian Lengen
Siyang Li
Lucas Macri
Emre Özülker
Dominic W. Pesce
Adam Riess
Martino Romaniello
Khaled Said
Nils Schöneberg
Dan Scolnic
Teresa Sicignano
Dorota M. Skowron
Syed A. Uddin
Licia Verde
Antonella Nota
Abstract
The direct, empirical determination of the local value of the Hubble constant (H0) has markedly advanced thanks to improved instrumentation, measurement techniques, and distance estimators. However, combining determinations from different estimators is non-trivial, due to correlated calibrations and different analysis methodologies. Using covariance weighting and leveraging the broad and comprehensive community of experts, we constructed a rigorous and transparent Distance Network (DN) to find a consensus value and uncertainty for the local H0. All critically reviewed the available data sets, spanning parallaxes, detached eclipsing binaries, masers, Cepheids, the TRGB, Miras, JAGB stars, SN Ia, Surface Brightness Fluctuations, SN II, the Fundamental Plane, and Tully-Fisher relations and voted for indicators to define a `baseline' DN and others to assess robustness and sensitivity of the results. We provide open-source software and data products to support full transparency and future extensions of this effort. Our conclusions: 1) Local H0 is robustly determined, with first-rank indicators internally consistent within their uncertainties; 2) A covariance-weighted combination yields an uncertainty of 1.1% (baseline) or 0.9% (all estimators); 3) The contribution from SNe Ia is consistent across four current compilations of optical magnitudes or using NIR-only magnitudes; 4) Removing either Cepheids or TRGB has minimal effect; 5) Replacing SNe Ia with galaxy-based indicators changes H0 by less than 0.1 km/s/Mpc, while doubling its uncertainty; 6) The baseline result is H0=73.50+/-0.81 km/s/Mpc. Compared to early Universe results, our result differs by 7.1sigma from flat ΛCDM with Planck+SPT+ACT and 5.0 sigma with BBN+BAO (DESI2). A networked approach is invaluable for enabling further progress in accuracy and precision without overreliance on any single method, sample or group.
