Globular Clusters with Dark Matter Halos. I. Initial Relaxation

In a series of two papers, we test the primordial scenario of globular cluster formation using results of high-resolution N-body simulations. In this first paper we study the initial relaxation of a stellar core inside a live dark matter minihalo in the early universe. Our dark matter-dominated globular clusters show features that are usually attributed to the action of the tidal field of the host galaxy. Among them are the presence of an apparent cutoff (tidal radius) or a break in the outer parts of the radial surface brightness profile and a flat line-of-sight velocity dispersion profile in the outskirts of the cluster. The apparent mass-to-light ratios of our hybrid (stars + dark matter) globular clusters are very close to those of purely stellar clusters. We suggest that additional observational evidence, such as the presence of obvious tidal tails, is required to rule out the presence of significant amounts of dark matter in present-day globular clusters.