Hubble tension tomography: BAO vs SnIa distance tension

TL;DR

This study examines the redshift dependence of the Hubble tension by comparing BAO and SnIa distances, revealing discrepancies at low redshifts and potential deviations from the standard cosmological model at high redshifts.

Contribution

It introduces a redshift tomography approach to analyze the Hubble tension and explores the need for re-evaluating distance calibration methods and potential high-redshift deviations.

Findings

Discrepancies between BAO and SnIa distances across redshifts.

Tension reduces at higher redshifts, indicating possible evolution of H0.

Hints of deviation from Planck18/$\\Lambda$CDM at $z\gtrsim 2$.

Abstract

We investigate the redshift dependence of the Hubble tension by comparing the luminosity distances obtained using an up-to-date BAO dataset (including the latest DESI data) calibrated with the CMB-inferred sound horizon, and the Pantheon+ SnIa distances calibrated with Cepheids. Using a redshift tomography method, we find: 1) The BAO-inferred distances are discrepant with the Pantheon+ SnIa distances across all redshift bins considered, with the discrepancy level varying with redshift. 2) The distance discrepancy is more pronounced at lower redshifts ($z \in [0.1,0.8]$) compared to higher redshifts ($z\in [0.8,2.3]$). The consistency of $\Lambda$CDM best fit parameters obtained in high and low redshift bins of both BAO and SnIa samples is investigated and we confirm that the tension reduces at high redshifts. Also a mild tension between the redshift bins is identified at higher redshifts for both the BAO and Pantheon+ data with respect to the best fit value of $H_0$ in agreement with previous studies which find hints for an 'evolution' of $H_0$ in the context of $\Lambda$CDM. These results confirm that the low redshift BAO and SnIa distances can only become consistent through a re-evaluation of the distance calibration methods. An $H(z)$ expansion rate deformation alone is insufficient to resolve the tension. Our findings also hint at a possible deviation of the expansion rate from the Planck18/$\Lambda$CDM model at high redshifts $z\gtrsim 2$. We show that such a deformation is well described by a high redshift transition of $H(z)$ like the one expressed by $\Lambda_s$CDM even though this alone cannot fully resolve the Hubble tension due to its tension with intermediate/low $z$ BAO data.