Determination of Remnant Merger Stage of Equal-Mass Disk Galaxies

There are many examples of merging galaxy found in observational astronomy, yet the timescales on which merging happens do not allow for one to study the evolution of galaxy merging of any one merger. Furthermore, there are no standard techniques for the identification of the stage of a galaxy mergers progress in the merging process. In this paper, simulations of merging galaxies are analyzed for a variety of collisions of two disk galaxies of equal mass, with the goal of finding a way to help distinguish galactic merger stage through the comparison of observable quantities. The morphology measurements Gini, M20, Concentration, Asymmetry, and Separation in conjunction with photometric color data output, namely the colors LIR/g and NUV-r, are used to this end. LIR/g and NUV-r were found to have a tight correlation with the star formation rate of the galaxies which is in turn related to the merger stage. The approach taken for the identification of merger stage is plotting data in a 3-dimensional observable parameter space with the goal of finding parameters and orientations of the plots to best isolate a merger stage within this space. Special attention is given to the remnant stage of the merger, however the techniques used in this paper could be extrapolated to all other stages as well.