Effect of Peak Absolute Magnitude of Type Ia Supernovae and Sound Horizon Values on Hubble Tension using DESI results

TL;DR

This study investigates how the degeneracy between the peak absolute magnitude of Type Ia supernovae and the sound horizon affects the Hubble tension, showing that adjusting these parameters can reduce the discrepancy between local and Planck measurements.

Contribution

It demonstrates the impact of $M$ and $r_d$ priors on Hubble constant estimates and identifies the least favored prior combination in the context of $ ext{Lambda}$CDM.

Findings

Degeneracy between $M$ and $r_d$ influences Hubble constant estimates.

Adjusting $r_d$ and $M$ can reduce Hubble tension to 1.2-2 sigma.

Certain prior combinations are less favored in $ ext{Lambda}$CDM.

Abstract

We apply data-motivated priors on the peak absolute magnitude of Type Ia supernovae ($M$) and the sound horizon at the drag epoch ($r_d$), to study how the $M-r_d$ degeneracy affects low redshift measurements of the Hubble constant, and then compare these estimates to the Planck estimated value of the Hubble constant. We use the data from Pantheon$+$, Cosmic Chronometers, and the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) Baryon Acoustic Oscillations (BAO) results for this purpose. We reaffirm the fact that there is a degeneracy between $M$ and $r_d$, and modifying the $r_d$ values to reconcile the discrepancy in Hubble constant values also requires a change in the peak absolute magnitude $M$. For certain $M$ and $r_d$ priors, the discrepancy is found to reduce to be as low as (1.2-2) $\sigma$ when considering the spatially flat $\Lambda$CDM model. We also notice that for our datasets considered, the Gaussian prior combination of $M \in \mathcal{N} (-19.253,0.027)$ (obtained from SH0ES) and $r_d \in \mathcal{N} (147.05,0.3)$ Mpc (determined from Planck CMB measurements) is least favored as compared to other prior combinations for the $\Lambda$CDM model.