The origin of globular cluster systems from cosmological simulations

TL;DR

This study uses cosmological simulations combined with semi-analytic models to explore the origins, properties, and distributions of globular cluster systems across different galaxy types, providing testable predictions about their formation history.

Contribution

It offers a comprehensive, self-consistent simulation-based analysis of globular cluster systems, revealing their formation epochs, metallicity bimodality, and dependence on galaxy properties.

Findings

Most GCs form in low-mass galaxies at high redshift (z > 3).

About 52% of galaxies with GCs show metallicity bimodality.

Elliptical galaxies have higher specific frequencies of GCs than spirals.

Abstract

We investigate the structural, kinematical, and chemical properties of globular cluster systems (GCSs) in galaxies of different Hubble types in a self-consistent manner based on high-resolution cosmological N-body simulations combined with semi-analytic models of galaxy and globular cluster (GC) formation. We focus on correlations between the physical properties of GCSs and those of their host galaxies for about 10^5 simulated galaxies located at the centres of dark matter halos (i.e. we do not consider satellite galaxies in sub-halos). Our principal results, which can be tested against observations, are as follows. The majority (about 90%) of GCs currently in halos are formed in low-mass galaxies at redshifts greater than 3 with mean formation redshifts of z = 5.7 (12.7 Gyrs ago) and 4.3 (12.3 Gyrs ago) for metal-poor GCs (MPC) and metal-rich GCs (MRCs), respectively. About 52 % of galaxies with GCs show clear bimodality in their metallicity distribution functions, though less luminous galaxies with M_B fainter than -17 are much less likely to show bimodality owing to little or no MRCs. The number fraction of MRCs does not depend on Hubble type but is generally smaller for less luminous galaxies. The specific frequencies (S_ N) of GCSs are typically higher in ellipticals (S_ N ~ 4.0) than in spirals (S_ N ~ 1.8), and higher again (S_N ~ 5.0) for galaxies located at the centers of clusters of galaxies. The total number of GCs per unit halo mass does not depend strongly on M_B or Hubble type of the host galaxy. The mean metallicities of MPCs and MRCs depend on M_B such that they are higher in more luminous galaxies, though the dependence is significantly weakerfor MPCs.