Abstract

We study the assembly of globular clusters (GCs) in 9 galaxy clusters using the cosmological simulation Illustris. GCs are tagged to individual galaxies at their infall time. The tidal removal of GCs from their galaxies and the distribution of the GCs within the cluster is later followed self-consistently by the simulation. The method relies on the simple assumption of a single power-law relation between halo mass (M-vir) and mass in GCs (M-GC) as found in observations. We find that the GCs specific frequency S-N as a function of V-band magnitude naturally reproduces the observed `U'-shape due to the combination of the power law M-GC-M-vir relation and the non-linear stellar mass (M-*)-halomass relation from the simulation. Additional scatter in the S-N values is traced back to galaxies with early infall times due to the evolution of the M-*-M-vir relation with redshift. GCs that have been tidally removed from their galaxies form the present-day intracluster component, from which about similar to 60 per cent were brought in by galaxies that currently orbit within the cluster potential. The remaining 'orphan' GCs are contributed by satellite galaxies with a wide range of stellar masses that are fully tidally disrupted at z = 0. This intracluster component is a good dynamical tracer of the dark matter potential. As a consequence of the accreted nature of most intracluster GCs, their orbits are fairly radial with a predicted orbital anisotropy beta >= 0.5. However, local tangential motions may appear as a consequence of localized substructure, providing a possible interpretation to the beta 0 values suggested in observations of M87.