EVOLUTION OF A SATELLITE DRAGGED IN BY DYNAMICAL FRICTION TOWARDS THE CENTER OF A GALAXY

The effects of dynamical friction on a satellite dragged in towards the center of a host elliptical galaxy have been studied mostly for the case of a satellite modeled as a rigid potential. However, under realistic conditions tidal distorsions of the satellite are expected to play an important role in the satellite–galaxy interaction. For the goal of describing such a complex stellar dynamical system, we have performed N-body simulations of the orbital evolution of a self–consistent, “live” satellite stellar system within a self–consistent, “live” host galaxy by means of the GADGET–2 code. As initial conditions, a King model for the satellite and an f^(ν) model for the host galaxy with dimensionless central potential W₀ = 7 and Ψ = 5, respectively, have been adopted; models of this type have found wide application to the description of globular clusters and elliptical galaxies. The satellite is initially placed on a quasi–circular orbit. The satellite slowly falls towards the center of the galaxy because of dynamical friction, while its mass and structure change in time as a result of the relevant tidal forces encountered along the orbit. We compare the orbital decay of this self–consistent live satellite to the orbital decay of a satellite modeled as a rigid King potential. We find that during the fall the structure of the satellite changes towards less concentrated configurations, which are interestingly well described, at any given time, as King models, but with smaller and smaller concentration parameter.