Angle–action estimation in a general axisymmetric potential




The usefulness of angle–action variables in galaxy dynamics is well known, but their use is limited due to the difficulty of their calculation in realistic galaxy potentials. Here we present a method for estimating angle–action variables in a realistic Milky Way axisymmetric potential by locally fitting a Stäckel potential over the region an orbit probes. The quality of the method is assessed by comparison with other known methods for estimating angle–action variables of a range of disc and halo-type orbits. We conclude by projecting the Geneva–Copenhagen survey into angle–action space.