For his thesis research, T.J. Cox ran a large suite of hydrodynamical galaxy merger simulations using the SPH code GADGET2. These simulations include dark matter halos, stellar particles, gas, star formation, and stellar feedback. My project uses this suite of simulations as a test bed for constructing models of the processes that occur during galaxy mergers. Using energy conservation and the virial theorem, along with toy models constructed for star formation and radiative losses during a merger, I construct a model which is capable of predicting the size, mass, and velocity dispersion of galaxy merger remnants given the progenitor properties and initial orbital parameters. The model works for a large range of masses, gas fractions, orbits, bulge fractions, and dark matter concentrations. This model provides a recipe that can be used in Semi-Analytic Models of galaxy formation (SAMs) to track the properties of a large population of galaxies throughout the history of the universe.

These figures show the values of the radius and velocity dispersion for the remnants in the suite of galaxy merger simulations. Values predicted by the model are plotted against values measured from the simulations. The line plotted is x=y and represents the relationship that would be expected for a perfect model.

We have submitted a paper to MNRAS which describes this model. You can find a preprint here.