ANATOMY OF A MERCER - A NUMERICAL-MODEL OF A754

A754 is a well-observed cluster of galaxies (z = 0.054) that exhibits a variety of morphological peculiarities. These include a bar of X-ray emission that is offset significantly from the galaxy distribution, a n elongated X-ray surface brightness distribution extending between tw o distinct peaks in the galaxy distribution, and an extremely nonisoth ermal and asymmetric intracluster medium temperature morphology. Using these observational constraints, we present a numerical hydro/N-body model of A754 in which two clusters (2.5:1 mass ratio) have merged nea rly in the plane of the sky less than 0.5 Gyr ago with an impact param eter of similar to 120 kpc and an impact velocity of similar to 2500 k m s(-1) (roughly the escape velocity of the primary cluster). Our mode ls allow us to identify the origin of A754's peculiar X-ray and temper ature morphologies, the underlying hydrodynamical processes that shape them, and their future evolution. We make detailed predictions for fu ture high-resolution X-ray spectroscopic observations (e.g., Astro-E). We discuss general properties of our models that will be characterist ic of off-axis mergers. In particular, we find significant nonthermal pressure support within the central region that could bias cluster mas s estimates. We find significant angular momentum imparted on the gas distribution in the cluster. We find that mixing of the subcluster gas components is an inefficient process, particularly at large radii. Fi nally, we find that subsequent dark matter-core passages result in an extended relaxation timescale.