Measuring the mass distribution in stellar systems
  One of the fundamental tasks of dynamical astronomy is to infer the
distribution of mass in a stellar system from a snapshot of the positions and
velocities of its stars. The usual approach to this task (e.g., Schwarzschild's
method) involves fitting parametrized forms of the gravitational potential and
the phase-space distribution to the data. We review the practical and
conceptual difficulties with this approach and describe a novel statistical
method for determining the mass distribution that does not require determining
the phase-space distribution of the stars. We show that this new estimator
out-performs other distribution-free estimators for the harmonic and Kepler
potentials.
