On the stability of quasi-equilibrium self-gravitating configurations in atidal field

The possibility that quasi-equilibrium self-gravitating galaxy-like configu rations exist in a tidal field is analyzed in this paper. More specifically , we address the question of how to predict initial configurations modeling galaxies that are able to survive environmental effects in a dense environ ment for roughly one Hubble time, provided that dynamical friction is negle cted. For simplicity, the configurations in the tidal field have been taken initially to be spherically symmetric and to have an isotropic velocity di spersion tensor (t-limited King spheres); they orbit inside steady state, s pherical halos, as those that presumably surround compact galaxy groups and galaxy clusters. Both circular and eccentric orbits have been considered. In both cases, the initial quasi-equilibrium configurations have been built up taking into account the external tidal field produced by the halo. It m odifies the escape velocity field of the configuration, compared with isola ted configurations. The survival of the configurations as they orbit inside the halos has been studied through N-body simulations. As a general result , it has been found that the bulk of the models are conserved along 12.5 Gy r of evolution and that the low rates of mass loss they experience are cons istent with those expected when the adiabatic protection hypothesis is at w ork. So, solutions for galaxy configurations in tidal quasi-equilibrium hav e been found, showing that tidal stripping in quiescent phases does not see m to be very important, unless the density of the galaxy environment at its formation had been much lower than that of the galaxy environment at the p oint of its orbit where the tidal perturbation is maximum.