H0 tension or M overestimation?

There is a strong discrepancy between the value of the Hubble parameter H-0(P) obtained from large scale observations such as the Planck mission, and the small scale value H-0(R), obtained from lowredshift supernovae (SNe). The value of the absolute magnitude M-Hom 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 M-Hom, 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, {M-P, M-R}, corresponding to different values of H-0, {H-0(P), H-0(R)}, obtained from the model independent consistency relation between H-0 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 {M-R, H-0(P)}, confirming previous studies, while with {M-P, H-0(P)} we find evidence of a small local void, which causes an overestimation of M-R with respect to M-P. An inhomogeneous model with the parameters {M-P, H-0(P)} fits the data better than a homogeneous model with {M-R, H-0(R)}, resolving the apparent H-0 tension. Using {M-P, H-0(P)}, we obtain evidence of a local inhomogeneity with a density contrast -0.140 +/- 0.042, extending up to a redshift of z(v) = 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).

Automated summary

This article discusses the discrepancy between the large-scale and small-scale values of the Hubble parameter H-0, and how to calibrate supernovae observations using the absolute magnitude. The study finds that different values of the absolute magnitude can strongly affect the evidence of local inhomogeneity.