Measurements of Ω and Λ from 42 High‐Redshift Supernovae

Why this mattered

TBD

Abstract

We report measurements of the mass density, ΩM, and cosmological-constant energy density, ΩΛ of the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 and 0.83, are fitted jointly with a set of supernovae from the Calán/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All supernova peak magnitudes are standardized using a SN Ia light-curve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8ΩM - 0.6ΩΛ ≈ - 0.2 ± 0.1 in the region of interest (ΩM ≲ 1.5). For a flat (ΩM + ΩΛ = 1) cosmology we find ΩflatM = 0.28+0.09-0.08 (1 σ statistical) +0.05-0.04 (identified systematics). The data are strongly inconsistent with a Λ = 0 flat cosmology, the simplest inflationary universe model. An open, Λ = 0 cosmology also does not fit the data well: the data indicate that the cosmological constant is nonzero and positive, with a confidence of P(Λ > 0) = 99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is tflat0 = 14.9+1.4-1.1(0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calán/Tololo sample and our high-redshift sample. Excluding those few supernovae that are outliers in color excess or fit residual does not significantly change the results. The conclusions are also robust whether or not a width-luminosity relation is used to standardize the supernova peak magnitudes. We discuss and constrain, where possible, hypothetical alternatives to a cosmological constant.

Related

• cite → Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant — Perlmutter et al. cite Riess et al. because both use high-redshift Type Ia supernova distances to infer cosmic acceleration and a positive cosmological constant.
• cite → Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds — Perlmutter et al. cite Schlegel et al. for Galactic dust reddening maps used to correct supernova brightness measurements.
• enables → SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION — High-redshift supernova measurements constrained Ω and Λ, giving WMAP7 an external distance-probe complement for fitting ΛCDM cosmological parameters.
• enables → Planck2013 results. XVI. Cosmological parameters — High-redshift supernova measurements constrained Ω and Λ, giving Planck 2013 an external benchmark for its CMB-derived cosmological parameters.
• enables → Planck 2018 results — High-redshift supernova constraints on Ω and Λ helped establish the ΛCDM parameter framework that Planck 2018 later measured precisely with CMB data.
• cite ← SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION — WMAP7 compared its CMB constraints on Ω and Λ with the Supernova Cosmology Project's Type Ia supernova evidence for low matter density and dark energy.
• cite ← First‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Determination of Cosmological Parameters — WMAP uses the high-redshift Type Ia supernova ΩM–ΩΛ constraints from Perlmutter et al. as complementary evidence for a low-density, dark-energy-dominated universe.
• cite ← Planck2013 results. XVI. Cosmological parameters — Planck 2013 cites the High-Z Supernova Team result as supernova evidence constraining ΩM and ΩΛ in the ΛCDM cosmological model.
• cite ← Planck 2018 results — Planck 2018 uses CMB constraints in the same ΛCDM cosmological framework whose accelerated-expansion evidence was established by high-redshift supernova measurements of Ω and Λ.

Sources

• DOI: https://doi.org/10.1086/307221
• OpenAlex: https://openalex.org/W1853767801