Prospects for Resolving the Hubble Constant Tension with Standard Sirens

Area of Science:

• Cosmology
• Astrophysics
• Observational Astronomy

Background:

• A significant tension exists between the Hubble constant (H₀) measured locally using Cepheid-supernovae and the value derived from cosmic microwave background (CMB) data within the standard cosmological model.
• This discrepancy, currently at a 3-sigma level, fuels debate on whether it indicates new physics or unaccounted systematic errors in measurements.

Purpose of the Study:

• To investigate how independent Hubble constant (H₀) estimates can arbitrate the tension between local and CMB measurements.
• To assess the consistency of different H₀ measurements using the posterior predictive distribution (PPD) under the standard cosmological model.

Main Methods:

• Utilized the inverse distance ladder approach, combining Baryon Oscillation Spectroscopic Survey (BOSS) baryon acoustic oscillation (BAO) data with the Pantheon supernova sample.
• Employed posterior predictive distribution (PPD) analysis to compare H₀ measurements derived from different cosmological probes.
• Projected the capabilities of future

Main Results:

• The inverse distance ladder H₀ posterior, derived from BOSS BAO and Pantheon supernovae, closely matches the Planck CMB H₀ estimate.
• The locally measured H₀ value is found to be a statistically unlikely outcome from the PPD generated by the combined BAO and supernova data.
• A future sample of approximately 50 binary neutron star standard siren events, detectable within a decade, is predicted to definitively adjudicate the H₀ tension.

Conclusions:

• Existing cosmological data, when analyzed via the inverse distance ladder, supports a Hubble constant value consistent with CMB measurements, challenging the local distance ladder result.
• Future standard siren observations offer a promising avenue to resolve the current Hubble constant discrepancy and potentially distinguish between new physics and systematic errors.