The Hubble Tension Revisited: Additional Local Distance Ladder Uncertainties

In a recent paper, we investigated possible systematic uncertainties related to the Cepheid color-luminosity calibration method and their influence on the tension between the Hubble constant as inferred from distances to Type Ia supernovae and the cosmic microwave background as measured with the Planck satellite. Here, we study the impact of other sources of uncertainty in the supernova distance ladder, including Cepheid temperature and metallicity variations, supernova magnitudes, and GAIA parallax distances. Using Cepheid data in 19 Type Ia supernova host galaxies from Riess et al., anchor data from Riess et al., and a set of recalibrated Milky Way Cepheid distances, we obtain H₀ = 71.9 ± 2.2 km s^-1 Mpc^-1, 2.0σ from the Planck value. Excluding Cepheids with estimated color excesses Ê(V-I) = 0.15 mag to mitigate the impact of the Cepheid color-luminosity calibration, the inferred Hubble constant is H₀ = 68.1 ± 2.6 km s^-1 Mpc^-1, removing the tension with the Planck value.