Optimal Moments for Velocity Fields Analysis

We describe a new method of overcoming problems inherent in peculiar velocity surveys by using data compression as a filter with which to separate large–scale, linear flows from small– scale noise that biases the results systematically. We demonstrate the effectiveness of our method using realistic catalogs of galaxy velocities drawn from N–body simulations. Our tests show that a likelihood analysis of simulated catalogs that uses all of the information contained in the peculiar velocities results in a bias in the estimation of the power spectrum shape parameter Γ and amplitude β, and that our method of analysis effectively removes this bias. We expect that this new method will cause peculiar velocity surveys to re–emerge as a useful tool to determine cosmological parameters.