Chemodynamic Evolution of Globular Cluster Systems

Abstract

We studied the relation between the ratio of rotational velocity to velocity dispersion and the metallicity ( /σv-metallicity relation) of globular cluster systems (GCSs) of disk galaxies by comparing the relation predicted from simple chemodynamic models for the formation and evolution of disk galaxies with the observed kinematical and chemical properties of their GCSs. We conclude that proto-disk galaxies underwent a slow initial collapse that was followed by a rapid contraction and derive that the ratio of the initial collapse timescale to the active star formation timescale is ~6 for our Galaxy and ~15 for M31. The fundamental formation process of disk galaxies was simulated based on simple chemodynamic models, assuming the conservation of their angular momentum. We suggest that there is a typical universal pattern in the /σv-metallicity relation of the GCSs of disk galaxies. This picture is supported by the observed properties of GCSs in the Galaxy and in M31. This relation would deviate from the universal pattern, however, if large-scale merging events took a major role in the chemodynamic evolution of galaxies and would reflect the epoch of such merging events. We discuss the properties of the GCS of M81 and suggest the presence of a past major merging event.