Numerical Models of NGC4038/9

There have been several attempts to model the ``Antennae'' in the literature. I will, however, concentrate this discussion on Toomre and Toomre's 1972 paper, Galactic Bridges and Tails and Barnes' 1988 paper, Encounters of Disk/Halo Galaxies.

Toomre and Toomre, 1972

Toomre and Toomre's 1972 paper is seen by many as the seminal work in this field, triggering a paradigm shift and establishing mergers and tidal interactions as respectable subjects for theoretical inquiry. Although there were several papers in the literature dealing with interacting galaxies at that time and despite the fact that their modeling of galaxies as central masses surrounded by disks of test particles was hardly novel, there were many virtues to the Toomres' work:

• their clear establishment of the necessary conditions for interactions to occur
• their lucid descriptions of bridge and tail making
• their analysis and reconstruction of several well known interacting systems
• their discussion of merger related phenomena which preempted observations made several years later.

Barnes, 1988

Barnes' paper, published 16 years after the Toomres' attempt, was the first to model interacting galaxies as fully 3 dimensional N-Body entities whose equations of motion were integrated in a self consistent manner. An important and telling addition to the simulation's armory was the presence of a massive dark halo; this would have an important effect on the evolution of the merger.

At the end of the main discussion, I will briefly review the work of Mihos, Richstone and Bothun and discuss the importance of model matching, as well as some of the observations that must be satisfied if the models are to be considered successful reconstructions.