### Abstract

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, α_{x} = P_{x}/ρ_{x}, must be less than -0.55 (95% confidence) for any value of Ω_{m}, and it is further limited to α_{x} < -0.60 (95% confidence) if Ω_{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 (α_{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 Ω_{iot} = Ω_{m} + Ω_{Δ} = 0.94 ± 0.26 (1 σ).

Original language | English (US) |
---|---|

Pages (from-to) | 74-79 |

Number of pages | 6 |

Journal | Astrophysical Journal |

Volume | 509 |

Issue number | 1 PART I |

DOIs | |

State | Published - Jan 1 1998 |

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### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Astrophysical Journal*,

*509*(1 PART I), 74-79. https://doi.org/10.1086/306495

}

*Astrophysical Journal*, vol. 509, no. 1 PART I, pp. 74-79. https://doi.org/10.1086/306495

**Supernova limits on the cosmic equation of state.** / Garnavich, Peter M.; Jha, Saurabh; Challis, Peter; Clocchiatti, Alejandro; Diercks, Alan; Filippenko, Alexei V.; Gilliland, Ronald Lynn; Hogan, Craig J.; Kirshner, Robert P.; Leibundgut, Bruno; Phillips, M. M.; Reiss, David; Riess, Adam G.; Schmidt, Brian P.; Schummer, Robert A.; Chris Smith, R.; Spyromilio, Jason; Stubbs, Chris; Suntzeff, Nicholas B.; Tonry, John; Carroll, Sean M.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Supernova limits on the cosmic equation of state

AU - Garnavich, Peter M.

AU - Jha, Saurabh

AU - Challis, Peter

AU - Clocchiatti, Alejandro

AU - Diercks, Alan

AU - Filippenko, Alexei V.

AU - Gilliland, Ronald Lynn

AU - Hogan, Craig J.

AU - Kirshner, Robert P.

AU - Leibundgut, Bruno

AU - Phillips, M. M.

AU - Reiss, David

AU - Riess, Adam G.

AU - Schmidt, Brian P.

AU - Schummer, Robert A.

AU - Chris Smith, R.

AU - Spyromilio, Jason

AU - Stubbs, Chris

AU - Suntzeff, Nicholas B.

AU - Tonry, John

AU - Carroll, Sean M.

PY - 1998/1/1

Y1 - 1998/1/1

N2 - 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, αx = Px/ρx, must be less than -0.55 (95% confidence) for any value of Ωm, and it is further limited to αx < -0.60 (95% confidence) if Ωm 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 (αx = -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 Ωiot = Ωm + ΩΔ = 0.94 ± 0.26 (1 σ).

AB - 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, αx = Px/ρx, must be less than -0.55 (95% confidence) for any value of Ωm, and it is further limited to αx < -0.60 (95% confidence) if Ωm 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 (αx = -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 Ωiot = Ωm + ΩΔ = 0.94 ± 0.26 (1 σ).

UR - http://www.scopus.com/inward/record.url?scp=22444452822&partnerID=8YFLogxK

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U2 - 10.1086/306495

DO - 10.1086/306495

M3 - Article

VL - 509

SP - 74

EP - 79

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 PART I

ER -