Dynamical evolution of massless particles in star clusters with NBODY6++GPU-MASSLESS: II. the long-term evolution of free-floating comets

Context. Comets, asteroids, planetesimals, free-floating planets, and brown dwarfs are continuously injected into the intracluster environment after expulsion from their host-planetary systems or binary system. The dynamics of large populations of such free-floating comets (ffcs) in a star cluster environment is not yet fully understood. Aims. We investigated the dynamical evolution of comet populations in star clusters and characterized the kinematics and ejection rates of ffc in a star cluster. Moreover, we determined whether a different initial energy distribution affects the mass segregation of the less massive population. Methods. We carried out simulations using the N-body code NBODY6++GPU-MASSLESS, which allows the fast integration of star clusters that contain large numbers of massless particles, to characterize the dynamics of populations of low-mass particles with sub-virial and super-virial distributions. Results. Comets do not participate in the mass-segregation process, similarly to planet-sized objects, regardless of their initial energy distribution. The latter slightly changed the whole dynamical evolution at the start of the simulation. We only observe an initial relaxation or collapse of the objects for super-virial and sub-virial ratios, respectively. The external regions of the ffcs population tend to be pulled back in the cluster core at the end of the simulation, suggesting the gravitational pull of the stars is pulling them back in the core. This phenomenon occurs at later times if the system is in virial equilibrium. Compared to less massive bodies, brown dwarfs experience more mass segregation. The inner regions tend to be more mixed with the stellar population.