Prospects for resolving the Hubble constant tension with standard sirens

TL;DR

This paper examines the discrepancy in Hubble constant measurements from different methods, showing current data favors CMB estimates but future binary neutron star observations could resolve the tension.

Contribution

It introduces a statistical framework to compare independent H0 measurements and assesses the potential of future standard siren data to resolve the tension.

Findings

Current data shows local and CMB H0 estimates are inconsistent.

Future binary neutron star observations can decisively distinguish between models.

Existing inverse distance ladder aligns with Planck CMB measurements.

Abstract

The Hubble constant ($H_0$) estimated from the local Cepheid-supernova (SN) distance ladder is in 3-$\sigma$ tension with the value extrapolated from cosmic microwave background (CMB) data assuming the standard cosmological model. Whether this tension represents new physics or systematic effects is the subject of intense debate. Here, we investigate how new, independent $H_0$ estimates can arbitrate this tension, assessing whether the measurements are consistent with being derived from the same model using the posterior predictive distribution (PPD). We show that, with existing data, the inverse distance ladder formed from BOSS baryon acoustic oscillation measurements and the Pantheon SN sample yields an $H_0$ posterior near-identical to the Planck CMB measurement. The observed local distance ladder value is a very unlikely draw from the resulting PPD. Turning to the future, we find that a sample of $\sim50$ binary neutron star "standard sirens" (detectable within the next decade) will be able to adjudicate between the local and CMB estimates.