The Acceleration of the Universe: Measurements of Cosmological Parameters from Type Ia Supernovae
The fate of the Universe, infinite expansion or a "big crunch", can be determined by measuring the redshifts and brightness of very distant supernovae. These provide a record of changes in the expansion rate of the Universe over the past several billion years. The mass density, ΩM, and cosmological-constant energy density, ΩΛ, are measured from a data-set consisting of 42 high-redshift 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 fit jointly with a set of supernovae from the Calán/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. We find ΩflatM = 0.28+0.09-0.08 (1σ 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 non-zero and positive, with a confidence of P(Λ > 0) = 99%, including the identified systematic uncertainties. Thus, the Universe is found to be accelerating, i.e., q0 = ΩM/2 - ΩΛ < 0. 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.
Publication Source (Journal or Book title)
Physica Scripta T
Goobar, A., Perlmutter, S., Aldering, G., Goldhaber, G., Knop, R., Nugent, P., Castro, P., Deustua, S., Fabbro, S., Groom, D., Hook, I., Kim, A., Kim, M., Lee, J., Nunes, N., Pain, R., Pennypacker, C., Quimby, R., Lidman, C., Ellis, R., Irwin, M., McMahon, R., Ruiz-Lapuente, P., Walton, N., Schaefer, B., Boyle, B., Filippenko, A., Matheson, T., Fruchter, A., Panagia, N., Newberg, H., & Couch, W. (2000). The Acceleration of the Universe: Measurements of Cosmological Parameters from Type Ia Supernovae. Physica Scripta T, 85, 47-58. Retrieved from https://digitalcommons.lsu.edu/physics_astronomy_pubs/4773