Global Cosmological Parameters Measured Using Classical Double Radio Sources

Daly, Ruth A.; Guerra, E. J.; Wan, Lin

Global Cosmological Parameters Measured Using Classical Double Radio Sources

Authors

Daly, Ruth A.

Guerra, E. J.

Wan, Lin

Description

Fourteen classical double radio galaxies with redshifts between zero and two were used to determine the cosmological parameters $Ω_m$, $Ω_Λ$, and $Ω_k$, where these are the normalized values of the mean mass density, cosmological constant, and space curvature at the present epoch. A low value of $Ω_m$ is obtained, and $Ω_m = 1$ is ruled out with 97.5% confidence. The low value of $Ω_m$ determined using the radio source method described here is also indicated by several independent tests. Thus, it appears that either a cosmological constant, or space curvature, is significant at the present epoch. This means that the universe is undergoing, or has recently undergone, a transition away from a state of matter domination and into a state where either a cosmological constant or space curvature is determining the expansion rate of the universe. The low value of $Ω_m$ presented here and by Guerra & Daly (1998) means that we can state with 97.5 % confidence that the universe will continue to expand forever.
To appear in "Fundamental Parameters in Cosmology", The proceedings of the XXXIIIrd Rencontres de Moriond, eds. J. Trân Thanh Vân & Y. Giraud-Heraud, (Paris, France: Editions Frontieres)