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New Galaxy-Group Analyses Put Local Expansion Rate at About 64 km/s/Mpc

Researchers inferred the rate by modeling galaxy motions in the Centaurus A and M81 groups rather than using traditional distance ladders.

Overview

  • The peer-reviewed studies, published in Astronomy & Astrophysics, report a local Hubble constant near 64 km/s/Mpc from a dynamical approach.
  • This value sits closer to the early-Universe Planck estimate than to recent distance-ladder results, indicating that measurement methods and local dynamics likely contribute to the Hubble tension.
  • The analyses map Centaurus A as a binary system with M83 and show the M81M82 group arranged in a planar structure with a distinct orientation pattern.
  • The team finds that the brightest member galaxies account for nearly all of each group's dynamical mass, reducing the need for large extended dark-matter halos in these cases.
  • The researchers plan to scale the method to larger volumes and incorporate future survey data such as 4MOST to test robustness and refine constraints on H0 and dark-matter inventories.