Supernova Limits on the Cosmic Equation of State Academic Article uri icon


  • We use Type la supernovae studied by the High-z Supernova Search Team to constrain the properties of an energy component that may have contributed to accelerating the cosmic expansion. We find that for a flat geometry the equation-of-state parameter for the unknown component, x = Px/x, must be less than -0.55 (95% confidence) for any value of m, and it is further limited to x < -0.60 (95% confidence) if m is assumed to be greater than 0.1. These values are inconsistent with the unknown component being topological defects such as domain walls, strings, or textures. The supernova (SN) data are consistent with a cosmological constant (x = -1) or a scalar field that has had, on average, an equation-of-state parameter similar to the cosmological constant value of -1 over the redshift range of z 1 to the present. SN and cosmic microwave background observations give complementary constraints on the densities of matter and the unknown component. If only matter and vacuum energy are considered, then the current combined data sets provide direct evidence for a spatially flat universe with iot = m + = 0.94 0.26 (1 ). 1998. The American Astronomical Society. All rights reserved.

published proceedings

  • The Astrophysical Journal

altmetric score

  • 14.432

author list (cited authors)

  • Garnavich, P. M., Jha, S., Challis, P., Clocchiatti, A., Diercks, A., Filippenko, A. V., ... Carroll, S. M.

citation count

  • 617

complete list of authors

  • Garnavich, Peter M||Jha, Saurabh||Challis, Peter||Clocchiatti, Alejandro||Diercks, Alan||Filippenko, Alexei V||Gilliland, Ron L||Hogan, Craig J||Kirshner, Robert P||Leibundgut, Bruno||Phillips, MM||Reiss, David||Riess, Adam G||Schmidt, Brian P||Schommer, Robert A||Smith, R Chris||Spyromilio, Jason||Stubbs, Chris||Suntzeff, Nicholas B||Tonry, John||Carroll, Sean M

publication date

  • December 1998