NMAGIC: Fast Parallel Implementation of a ξ-Made-To-Measure Algorithm for Modeling Observational Data

We describe a made-to-measure algorithm for constructing N-body models of stellar systems from observational data (χ^2M2M), extending earlier ideas by Syer and Tremaine. The algorithm properly accounts for observational errors, is flexible, and can be applied to various systems and geometries. We implement this algorithm in a parallel code NMAGIC and carry out a sequence of tests to illustrate its power and performance: (i) We reconstruct isotropic Hernquist models from density moments and projected kinematics and recover the correct differential energy distribution and intrinsic kinematics. (ii) We build self-consistent oblate isotropic and maximum rotator models having the correct projected kinematics. (iii) We create a non-rotating and a figure rotating triaxial particle model, and reproduce the projected kinematics of the tumbling stellar system by a non-rotating system of the same intrinsic shape. From these tests we comment on the dependence of the results on the initial model, the geometry, the amount of available data, and the technical parameters in the algorithm.