N-body simulations of slow tidal encounters and the formation of galactic halos

An investigation of slow hyperbolic encounters between a 250-body spherical system and a few-body perturber of comparable total mass showed that the tidal effect on a system with a decreasing M(R)/R profile extends an inner region of constant M/R ratio to 50-70% of the bound mass. The tidal effects include gradual stripping of up to one-third of the stars from the regions outside the half-radius R(h), and retention of the flat inner profile under tandem encounters while the outer parts are continuously stripped. It is suggested that the regions of flat rotation curves in halos around spiral galaxies correspond to the inner parts of larger, dark, protohalos which underwent slow tidal encounters during their hierarchical gravitational clustering process.