Dynamical Modeling of Galaxy Mergers using Identikit
  We present dynamical models of four interacting systems: NGC 5257/8, The
Mice, the Antennae, and NGC 2623. The parameter space of the encounters are
constrained using the Identikit model-matching and visualization tool.
Identikit utilizes hybrid N-body and test particle simulations to enable rapid
exploration of the parameter space of galaxy mergers. The Identikit-derived
matches of these systems are reproduced with self-consistent collisionless
simulations which show very similar results. The models generally reproduce the
observed morphology and \HI\ kinematics of the tidal tails in these systems
with reasonable properties inferred for the progenitor galaxies. The models
presented here are the first to appear in the literature for NGC 5257/8 and NGC
2623, and The Mice and the Antennae are compared with previously published
models. Based on the assumed mass model and our derived initial conditions, the
models indicate the four systems are currently being viewed 175-260 Myr after
first passage and cover a wide range of merger stages. In some instances there
are mismatches between the models and the data (e.g., in the length of a tail);
these are likely due to our adoption of a single mass model for all galaxies.
Despite the use of a single mass model, these results demonstrate the utility
of Identikit in constraining the parameter space for galaxy mergers when
applied to real data.
