Galactic Dark Matter Halos and Globular Cluster Populations. III: Extension to Extreme Environments

Understand

The total mass M_GCS in the globular cluster (GC) system of a galaxy is empirically a near-constant fraction of the total mass M_h = M_bary + M_dark of the galaxy, across a range of 10^5 in galaxy mass.

• This trend is radically unlike the strongly nonlinear behavior of total stellar mass M_star versus M_h.
• We discuss extensions of this trend to two more extreme situations: (a) entire clusters of galaxies, and (b) the Ultra-Diffuse Galaxies (UDGs) recently discovered in Coma and elsewhere.
• Our calibration of the ratio \eta_M = M_GCS / M_h from normal galaxies, accounting for new revisions in the adopted mass-to-light ratio for GCs, now gives \eta_M = 2.9 \times 10^{-5} as the mean absolute mass fraction.