The Pantheon+ Analysis: Cosmological Constraints

Abstract

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 w 0CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s−1 Mpc−1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 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 w 0 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 w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 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 H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

The Pantheon+ Analysis: SuperCal-fragilistic Cross Calibration, Retrained SALT2 Light-curve Model, and Calibration Systematic Uncertainty

“…In this work we do not alter the CALSPEC spectra to assess CALSPEC related systematic uncertainties. For the CALSPEC systematic uncertainty and impact on cosmological analysis see Brout et al (2022).…”

“…In order to maximize statistical leverage and minimize the impact of calibration errors when constraining cosmological parameters, recent analyses have combined SNe from multiple different photometric systems. In this paper, we perform an up-to-date recalibration of photometric systems used in the Pantheon+ sample (Scolnic et al 2022) and cosmological analysis (Brout et al 2022), and propagate these changes through light-curve model training/fitting and to cosmological inference.…”

“…This paper is a companion to a suite of papers (e.g., S22; Dhawan et al 2020;Brownsberger et al 2021;Carr et al 2021;Popovic et al 2021;Peterson et al 2022) leading up to the Pantheon+ cosmological analysis (Brout et al 2022), which contains the measurements of cosmic acceleration, dark energy, and dark matter, and a SH0ES distance-ladder Hubble constant analysis (Riess et al 2022). This work focuses solely on the cross calibration of the samples and associated systematic uncertainty.…”

The Pantheon+ Analysis: Evaluating Peculiar Velocity Corrections in Cosmological Analyses with Nearby Type Ia Supernovae

“…Previous works have studied several PV catalogs and methods (Boruah et al 2021;Blakeslee et al 2021;Rahman et al 2021), but we aim to cover a more diverse range of catalogs here. Importantly, the analysis done here uses the same sample that will be used for both Riess et al (2022;SH0ES), Brout et al (2022), andScolnic et al (2022;hereafter Pantheon+). This paper is a companion paper to Carr et al (2022), which does a full review of all redshift samples and also derives the 2M++ velocities used in this work.…”

“…Although this statistic is often referred to as a χ 2 in the literature, we call it X 2 as we make no claims about its distribution under a null hypothesis. This statistic does not take account of correlations present in the data from effects such as calibration, bias correction models, or MW extinction (see Brout et al 2022 for a full analysis). However, as we are principally interested in the diagonal scatter caused by PVs, these effects have little impact on our final conclusions.…”