Relatore
Descrizione
The original formulation of dynamical friction (DF), developed for a particle moving in a infinite and media, delivers accurate predictions of sinking time scales for a test mass in a broad class of models, while failing in several other cases. $N-$body simulations hint at a breakdown of the original formalism for massive satellites sinking in the host galaxy, or compact objects in cores. Semi-analytical treatment of DF have softened this discrepancy, even though a comparison with simulations is still missing, due to the interplay between DF and the tidal effects on extended systems. We performed $N-$body simulations of a satellite orbiting in spherical galaxy model, for different values of the initial orbital eccentricity, satellite mass, scale radius and velocity anisotropy of the host. We adopt a scheme where the self-consistent interaction among the particles representing the galaxy can be substituted with the effect of a static smooth potential and a semi-analytical DF to disentangle the contributions to the friction due the trailing wake from that of the tidal tails. The satellite can be modeled either with $N_{\rm sat}$ particles or represented by a particle with an effective extension parametrized by the form of the force exchanged with the other simulation particles. We find that, at fixed galaxy model and satellite mass, the more extended is the satellite the weaker is the effect of DF in particular for orbital eccentricities $\gtrsim0.6$. Independently on the satellite mass or size, DF is less efficient in systems dominated by low angular momentum orbits.
| Sessione | Evoluzione delle galassie |
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