Prospects for galaxy-mass relations from the 6dF Galaxy Survey

We develop new methods to study the properties of galaxy redshift surveys and radial peculiar velocity surveys, both individually and combined. We derive the Fisher information matrix for redshift surveys, including redshift distortions and stochastic bias. We find exact results for estimating the marginalized accuracy of a two-parameter measurement of the amplitude of galaxy clustering, A(g), and the distortion parameter beta. The Fisher matrix is also derived for a radial peculiar velocity survey and we discuss optimization of these surveys for equal time-scales. The Fisher supermatrix, combining both surveys, is derived. We apply these results to investigate the 6 degree Field (6dF) Galaxy Survey, currently underway on the UK Schmidt Telescope (UKST). The survey will consist of similar to10(5) K-band selected galaxies with redshifts and a subset of similar to15 000 galaxies with radial peculiar velocities. We find for the redshift survey that we can measure the three parameters A(g), Gamma and beta to about 5 per cent accuracy, but will not be able to detect the baryon abundance or the matter-galaxy correlation coefficient, r(g). The peculiar velocity survey will jointly measure the velocity amplitude A(v) and Gamma to around 25 per cent accuracy. A conditional estimate of the amplitude A(V) alone can be made to 5 per cent. When the surveys are combined however, the major degeneracy between beta and r(g) is lifted and we are able to measure A(g), Gamma, beta and r(g) to the 2 per cent level, significantly improving on current estimates. Finally, we consider scale dependence of r(g) and the biasing parameter b. We find that measurements for these averaged over logarithmic passbands can be constrained to the level of a few per cent.