On spatial distributions of old globular clusters in clusters of galaxies

Abstract

We investigate structural properties of old, metal-poor globular clusters (GCs) formed at high redshifts (z > 6) and located inside and outside virialized galaxy-scale haloes in clusters of galaxies with the total masses of M^L based on high-resolution cosmological simulations with models of GC formation. We mainly derive the parameter dependences of physical properties of intracluster GCs (ICGCs) based on the results of 14 cluster models. Our principle results are summarized as follows. (1) ICGCs are formed as a result of tidal stripping of GCs initially within galaxy-scale haloes during hierarchical growth of clusters via halo merging. These ICGCs comprise 20-40 per cent of all GCs in clusters with 1.0 × 1014 M⊙ ≤ M CL ≤ 6.5 × 1014 M⊙ and the number fraction of ICGCs does not depend on MCL for the above cluster mass range. (2) The projected radial density profiles (ΣGC) of ICGCs in clusters with different McL can be diverse, though ICGCs have inhomogeneous, asymmetric and somewhat elongated distributions in most models. If Σ(R) ∝ Rα, α ranges from ≈-1.5 to ≈ -2.5 for GCs in clusters with the above mass range. (3) Although total number of GCs within the central 0.05 Mpc (NGC,0.05) and 0.2 Mpc (NGC,0.2) are diverse in different clusters, they can depend weakly on MCL in such a way that both NGC,0.05 and NGC,0.2 are likely to be larger for clusters with larger McL. (4) Total number of GCs per cluster masses (specific frequency of GCs for clusters of galaxies) are more likely to be larger in more massive clusters, mainly because a larger number of earlier virialized objects can be located in more massive clusters. (5) Radial density distributions of all GCs including ICGCs and galactic GCs have steeper profiles than those of the background dark matter haloes in the central regions of clusters (R< 200 kpc) with different MCL. (6) Spatial distributions of old GCs in clusters can depend on the truncation epoch of GC formation (ztrun) such that they can be steeper and more compact in the models with higher Ztrun. (7) The mean metallicity of ICGCs in a cluster can be smaller than that of GCs within the cluster member galaxy-scale haloes by ∼0.3 in [Pe/H]. Metallicity distribution functions (MDPs) of ICGCs show peak values around [Pe/H] ∼ -1.6 and do not have remarkable bimodality. © 2006 RAS.