Global Cosmological Parameters Determined Using Classical Double Radio Galaxies

A sample of 20 powerful extended radio galaxies with redshifts between zeroand two were used to determine constraints on global cosmological parameters.Data for six radio sources were obtained from the VLA archive, analyzed, andcombined with the sample of 14 radio galaxies used previously by Guerra & Dalyto determine cosmological parameters. The new results are consistent with ourprevious results, and indicate that the current value of the mean mass densityof the universe is significantly less than the critical value. A universe with$\Omega_m$ in matter of unity is ruled out at 99.0% confidence, and the bestfitting values of $\Omega_m$ in matter are $0.10^{+0.25}_{-0.10}$ and$-0.25^{+0.35}_{-0.25}$ assuming zero space curvature and zero cosmologicalconstant, respectively. The radio properties of each source are also used to determine the density ofthe gas in the vicinity of the source, and the beam power of the source. Thesix new radio sources have physical characteristics similar to those found forthe original 14 sources. The density of the gas around these radio sources istypical of gas in present day clusters of galaxies. The beam powers aretypically about $10^{45} {erg s}^{-1}$.Comment: Submitted to ApJ, LaTex, 10 pages of text, plus 4 tables and 5 figures in documen