A Systematic Analysis of Caustic Methods for Galaxy Cluster Masses

We quantify the expected observed statistical and systematic uncertainties of the escape velocity as a measure of the gravitational potential and total mass of galaxy clusters. We focus our attention on low redshift (z 25, the scatter in the escape velocity mass is dominated by projections along the line-of-sight. Algorithmic uncertainties from the determination of the projected escape velocity profile are negligible. We quantify how target selection based on magnitude, color, and projected radial separation can induce small additional biases into the escape velocity masses. Using Ngal = 150 (25), the caustic technique has a per cluster scatter in ln (M|M₂00) of 0. 3 (0. 5) and bias 1+/-3% (16+/-5%) for clusters with masses > 10¹4Mₛolar at z<0. 15.