On the origin of mass-metallicity relations, blue tilts and scaling relations for metal-poor globular cluster systems

Abstract

We investigate formation processes and physical properties of globular cluster systems (GCSs) in galaxies based on high-resolution cosmological simulations with globular clusters. We focus on metal-poor clusters (MPCs) and correlations with their host galaxies by assuming that MPC formation is truncated at a high redshift. We find that the correlation between mean metallicities (Zgc) of MPCs and their host galaxy luminosities (L) flattens from to 0. We also find that the observed relation in MPCs can be reproduced well in the models with at when, if mass-to-light ratios are assumed to be constant at. A flatter at is found to be required to explain the observed relation for constant mass-to-light ratio models with lower. However, better agreement with the observed relation is found for models with different mass-to-light ratios between and 0. It is also found that the observed colour-magnitude relation of luminous MPCs (i.e. 'blue tilts') may only have a small contribution from the stripped stellar nuclei of dwarf galaxies, which have nuclei masses that correlate with their total mass at. The simulated blue tilts are found to be seen more clearly in more massive galaxies, which reflects the fact that more massive galaxies at are formed from a larger number of dwarfs with stellar nuclei formed at. The half-number radii (Re) of GCSs, velocity dispersions of GCSs (σ) and their host galaxy masses (Mh) are found to be correlated with one another such that and. Based on these results, we discuss the link between hierarchical merging histories of galaxies and the physical properties of MPCs, the origin of the relation and non-homology of GCSs. © 2007 RAS.