Abstract: 

In this seminar the speaker will talk about the "dynamical friction" in galaxy halos. He will focus first on Chandrasekhar approach, enlightening its limitationas and successes. Next he will present alternative approaches like the linear perturbation theory (e.g Binney & Tremaine, 1987) and N-body simulations. Part of this work (Master thesis and PhD project), revolves around increasing the complexity of commonly used dynamical friction models by changing halo properties (homogeneity vs. inhomogeneity), halo density profiles (core vs. cusp) and adding more than one perturber. This study pursue the goal of fully analysing the halo perturbation modes produced by interactions with one or several perturbers. N-body simulations are being used as they allow to self-consistently study the individual and collective effects, and, depending on the particles number, also reproduce low amplitude perturbation modes. Finally it is planned to study the colective effects of many perturbers and its relation with the increase or decrease on the dynamical friction and, so, the infall time of satellites.