Interacting Binary Galaxies. IV. Simulations, Masses, and Spatial Orientations for NGC 1587/1588 and NGC 7236/7237

We describe here our successful efforts to match interaction models to all of the available data for two pairs of interacting binary galaxies, Nos. 99 and 564 in the Karachentsev catalog of isolated pairs. One of two companion papers (Paper II) describes the physical model and simulation technique, while a second companion paper (Paper III) presents the observational data for these two binaries. That the combined spectroscopic and photometric observations for a binary can be reproduced by an appropriate projection of a particular numerical simulation of the system provides convincing proof of both the gravitational origin of the observed disturbances and of the validity of simple Newtonian gravity on a 10 kpc scale. Exercising very few assumptions, we have been able to reconstruct the three-dimensional spatial orientation of each pair and thereby to measure its total mass. Constraints have been placed not only on the masses of the galaxies, but also on their internal dynamical configurations and on the properties of their relative orbit. For the two pairs, K99 and K564, the total masses that we derive are quite reasonable and yield M/L values near 10. Given the success with which these simulations have matched all available data, we conclude that the observed disturbances in rotation velocity and luminosity distribution for these binary galaxies are entirely consistent with the merger hypothesis. Distortions include U-shaped rotation profiles and one-sided luminosity distentions. These tidal perturbations provide solid observational evidence of tidal friction in action.