Cosmological Model Insensitivity of Local H₀ from the Cepheid Distance Ladder

The observed tension (∼9% difference) between the local distance ladder measurement of the Hubble constant, H 0 , and its value inferred from the cosmic microwave background could hint at new, exotic, cosmological physics. We test the impact of the assumption about the expansion history of the universe ( ) on the local distance ladder estimate of H 0 . In the fiducial analysis, the Hubble flow Type Ia supernova (SN Ia) sample is truncated to z < 0.15, and the deceleration parameter ( q 0 ) is fixed to −0.55. We create realistic simulations of the calibrator and Pantheon samples, and account for a full systematics covariance between these two sets. We fit several physically motivated dark-energy models, and derive combined constraints from calibrator and Pantheon SNe Ia and simultaneously infer H 0 and dark-energy properties. We find that the assumption on the dark-energy model does not significantly change the local distance ladder value of H 0 , with a maximum difference (Δ H 0 ) between the inferred value for different models of 0.47 km , i.e., a 0.6% shift in H 0 , significantly smaller than the observed tension. Additional freedom in the dark-energy models does not increase the error in the inferred value of H 0 . Including systematics covariance between the calibrators, low-redshift SNe, and high-redshift SNe can induce small shifts in the inferred value for H 0 . The SN Ia systematics in this study contribute ≲0.8% to the total uncertainty of H 0 .