A Reanalysis of the Latest SH0ES Data for H0: Effects of New Degrees of Freedom on the Hubble Tension

Abstract

We reanalyze in a simple and comprehensive manner the recently released SH0ES data for the determination of H0. We focus on testing the homogeneity of the Cepheid+SnIa sample and the robustness of the results in the presence of new degrees of freedom in the modeling of Cepheids and SnIa. We thus focus on the four modeling parameters of the analysis: the fiducial luminosity of SnIa MB and Cepheids MW and the two parameters (bW and ZW) standardizing Cepheid luminosities with period and metallicity. After reproducing the SH0ES baseline model results, we allow for a transition of the value of any one of these parameters at a given distance Dc or cosmic time tc, thus adding a single degree of freedom in the analysis. When the SnIa absolute magnitude MB is allowed to have a transition at Dc≃50 Mpc (about 160 Myrs ago), the best-fit value of the Hubble parameter drops from H0=73.04±1.04 km s−1 Mpc−1 to H0=67.32±4.64 km s−1 Mpc−1 in full consistency with the Planck value. Additionally, the best-fit SnIa absolute magnitude MB> for D>Dc drops to the Planck inverse distance ladder value MB>=−19.43±0.15, while the low distance best fit MB< parameter remains close to the original distance ladder calibrated value MB<=−19.25±0.03. Similar hints for a transition behavior is found for the other three main parameters of the analysis (bW, MW and ZW) at the same critical distance Dc≃50 Mpc, even though in that case, the best-fit value of H0 is not significantly affected. When the inverse distance ladder constraint on MB> is included in the analysis, the uncertainties for H0 reduce dramatically (H0=68.2±0.8 km s−1 Mpc−1), and the MB transition model is strongly preferred over the baseline SH0ES model (Δχ2≃−15, ΔAIC≃−13) according to the AIC and BIC model selection criteria.