Formation of Intracluster and Intercluster Globular Clusters

Abstract

Based on high-resolution cosmological simulations with models of GC formation at high redshifts (z > 6), we investigate structural and kinematical properties of intracluster globular clusters (ICGCs) that are located outside virialized galaxy-scale halos yet within clusters of galaxies with the total masses of M_CL. We find that these ICGCs are formed as a result of tidal stripping of GCs initially within galaxy-scale halos during hierarchical growth of clusters via halo merging. We also find that ICGCs comprise 20–40% of all GCs in clusters with 1.0 × 10¹⁴ M_⊙ < M_CL < 6.5 × 10¹⁴ M_⊙. Furthermore, the projected radial density profiles (Σ_GC) of all GCs in clusters with different M_CL are found to be quite diverse. If Σ_GC (R) ∝ R^α, α ranges from ≈ -1.5 to ≈ -2.5 for GCs in clusters with the above mass range. Σ_GC is demonstrated to be dependent on the truncation epoch of GC formation at high redshifts by cosmological processes such as reionization. About ~ 1% of all GCs formed before z>6 can not be within any galaxy-scale halos and thus identified as intercluster or intergroup (or intergalactic) GCs.