Theoretical and methodological review of dynamical friction in major mergers

Abstract

We investigate the process of dynamical friction from the point of view of the dynamics of galaxy mergers. We are particularly interested in providing an accurate formula for the merger time between galactic halos of similar mass, also known as major mergers. We have reviewed the theoretical foundations of this mechanism, as well as used 605 isolated simulations of binary collisions of galaxies to test a new non-separable expression for the merger timescale. Our study reveals some plausible reasons why merger time formulas existing in the literature may not perform successfully for major mergers, related to both the theory and the methodology applied in the analysis of numerical results.