The Pantheon+ Analysis: Cosmological Constraints

We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω_M = 0.334 ± 0.018 from SNe Ia alone. For a flat w₀CDM model, we measure w₀ = −0.90 ± 0.14 from SNe Ia alone, H₀ = 73.5 ± 1.1 km s⁻¹ Mpc⁻¹ when including the Cepheid host distances and covariance (SH0ES), and w₀ = -0.978_-⁺_0.031^0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w₀ values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w₀w_aCDM universe, and measure w_a = -0.1_-⁺_2.0^0.9 from Pantheon+ SNe Ia alone, H₀ = 73.3 ± 1.1 km s⁻¹ Mpc⁻¹ when including SH0ES Cepheid distances, and w_a = -0.65_-⁺_0.32^0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H₀. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.