Breaking the Degeneracy of Cosmological Parameters in Galaxy Redshift Surveys

The measurement of cosmological parameters is investigated in arepresentation of the least-action method that uses a redshift-space dataset tosimultaneously constrain the real-space fields $\delta$,$\b v$. This method isrobust in recovering the entire evolution of the matter density contrast andpeculiar velocities of galaxies in real space from current galaxy redshiftsurveys. The main strength of the method is that it permits us to break thedegeneracy of the parameters $b$ and $\Omegam$ (customarily measured in theratio $\beta\equiv \Omegam^{0.6}/b$ from redshift-space distortions), and theseare evaluated in the current context separately. The procedure provides asimple numerical means to extract as much information as possible from a givensample, in the simplest linear bias model, before resorting to cosmiccomplementarity to resolve the degeneracy in the measurement of $\Omegam$. Thesame premise applies to more sophisticated choices of bias models. We constructa likelihood parameter $\lambda(b,\Omegam)$ to evaluate the relative likelihoodof different values of $b$ and $\Omegam$. The method is applied to the \irasredshift survey with a low-resolution Gaussian smoothing length of 1200 \kmwithin a spherical region $x_{\rm max} \sim 15,000$ \km and the reconstructedvelocity field is then compared with POTENT-reconstructed velocities from theMark III radial-velocity dataset within a radius $\sim 5000$ \km, which havebeen suitably prepared to account for Malmquist bias and other systematicerrors. The analysis yields a likelihood for the parameters that is overallconsistent with $\Omegam\approx 0.3$ and $b\approx 1.1$, thus lending supportto a non-vanishing cosmological constant $\Omega_{\Lambda}\approx 0.7$ in aflat universe.Comment: 15 pages, 10 figures, uses mn.sty, one section added and minor revisions, to appear ApJ Jan 0