N-body simulations of globular cluster tides

We present N-body simulations of globular clusters, in orbits around the Ga laxy, in order to study quantitatively and geometrically the tidal effects they encounter. The clusters are modelised with multi-mass King-Michie mode ls (Michie 1963), including mass segregation at initial conditions. The Gal axy is modelled as realistic as possible, with three components: bulge, dis k and dark halo. The main finding is that there exist two giant tidal tails around the globuler cluster in permanence along its orbit, whatever this o rbit. The length of these tails is of the order of 5 tidal radii, or greate r. The escaped stars are distributed radially as a power law in density, wi th a slope of -4. The tails present substructures, or clumps, that are the relies of the strongest shocks. Due to the compressive disk-shocking, the c lusters display a prolate shape whose major axis is precessing around the z axis. The tails are preferentially formed by the lowest mass stars, as exp ected, so that the tidal truncation increases mass segregation, internal ro tation of the cluster increases the mass loss. The flattening of dark matte r cannot influence significantly the dynamics of the clusters, The orientat ion and the strength of the tidal tails are signatures of the last disk cro ssing, so that observed tidal tails can constrain strongly the cluster orbi t and the galactic model (vertical scale of the disc).