H tension or M overestimation?

Abstract

There is a strong discrepancy between the value of the Hubble parameter H0P obtained from large scale observations such as the Planck mission, and the small scale value H0R, obtained from low redshift supernovae (SNe). The value of the absolute magnitude MHom used as prior in analyzing observational data is obtained from low-redshift SNe, assuming a homogeneous Universe, but the distance of the anchors used to calibrate the SNe to obtain M would be affected by a local inhomogeneity, making it inconsistent to test the Copernican principle using MHom, since M estimation itself is affected by local inhomogeneities. We perform an analysis of the luminosity distance of low redshift SNe, using different values of M, { MP, MR} , corresponding to different values of H, {H0P,H0R}, obtained from the model independent consistency relation between H and M which can be derived from the definition of the distance modulus. We find that the value of M can strongly affect the evidence of a local inhomogeneity. We analyze data from the Pantheon catalog, finding no significant statistical evidence of a local inhomogeneity using the parameters {MR,H0R}, confirming previous studies, while with {MP,H0P} we find evidence of a small local void, which causes an overestimation of MR with respect to MP. An inhomogeneous model with the parameters {MP,H0P} fits the data better than a homogeneous model with {MR,H0R}, resolving the apparent H tension. Using {MP,H0P}, we obtain evidence of a local inhomogeneity with a density contrast - 0.140 ± 0.042 , extending up to a redshift of zv= 0.056 ± 0.0002 , in good agreement with recent results of galaxy catalogs analysis (Wong et al. in The local hole: a galaxy under-density covering 90 mpc, 2021).