{"doi":"10.1086/307221","title":"Measurements of Ω and Λ from 42 High‐Redshift Supernovae","abstract":"Here we report measurements of the mass density, Ω<sub>M</sub>, and cosmological-constant energy density, Ω<sub>Λ</sub>, 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 0.8Ω<sub>M</sub>-0.6Ω<sub>Λ</sub>≈-0.2±0.1 in the region of interest (Ω<sub>M</sub>≲1.5). For a flat (Ω<sub>M</sub>+Ω<sub>Λ</sub>=1) cosmology we find Ω$_{M}^{flat}$=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 t$_{0}^{flat}$=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.","journal":"The Astrophysical Journal","year":1999,"id":4504,"datarank":15.84078998629425,"base_score":9.786672797944293,"endowment":9.786672797944293,"self_citation_contribution":1.4680009196916441,"citation_network_contribution":14.372789066602607,"self_endowment_contribution":1.4680009196916441,"citer_contribution":14.372789066602607,"corpus_percentile":96.9,"corpus_rank":385,"citation_count":17794,"citer_count":174,"citers_with_citation_signal":174,"citers_with_endowment":174,"datacite_reuse_total":0,"is_dataset":false,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"1999-06-01","authors":[{"id":20662,"name":"G. Aldering","orcid":null,"position":1,"is_corresponding":false},{"id":45644,"name":"G. Goldhaber","orcid":null,"position":2,"is_corresponding":false},{"id":45645,"name":"R. A. 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Nunes","orcid":"0000-0002-3837-6914","position":14,"is_corresponding":false},{"id":45656,"name":"R. Pain","orcid":"0000-0003-4016-6067","position":15,"is_corresponding":false},{"id":45657,"name":"C. R. Pennypacker","orcid":null,"position":16,"is_corresponding":false},{"id":45658,"name":"R. Quimby","orcid":"0000-0001-9171-5236","position":17,"is_corresponding":false},{"id":45659,"name":"Christopher Lidman","orcid":"0000-0003-1731-0497","position":18,"is_corresponding":false},{"id":45660,"name":"R. S. Ellis","orcid":null,"position":19,"is_corresponding":false},{"id":45661,"name":"M. Irwin","orcid":null,"position":20,"is_corresponding":false},{"id":45662,"name":"R. G. McMahon","orcid":"0000-0001-8447-8869","position":21,"is_corresponding":false},{"id":45663,"name":"P. Ruiz‐Lapuente","orcid":null,"position":22,"is_corresponding":false},{"id":94602,"name":"S. L. Vogl","orcid":null,"position":23,"is_corresponding":false},{"id":45665,"name":"B. 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