Dynamical Simulations of the First Globular Clusters

Abstract A Milky Way–like halo is simulated with tidally limited star clusters inserted in the dark matter halos present at high redshift. An n -body code augmented with velocity relaxation in the star clusters evolves the system. The stripped stars and remnant clusters that began in the lower mass subhalos have a distribution somewhat more extended than the dark matter halo, with a mean galactic radius of about 60 kpc inside 150 kpc, whereas the distribution of all stripped stars and clusters is more centrally concentrated than the dark matter. The clusters from low mass subhalos, those with a peak circular velocity of 12–18 , also produce most of the population’s thin stellar streams. Together these suggest a search strategy for extremely metal-poor cluster stars and their remnants. The dependence of the stellar population distribution on subhalo mass is not seen in simulations that start clusters at lower redshift. The half mass radii of the clusters are set by the tidal fields of the initial subhalo, “dwarf galaxy” location, which causes the average half mass–radius to decrease with increasing redshift of formation. Starting clusters at greater than redshift 4 leads to cluster half mass radii approximately as seen in the Milky Way.