Various galaxy properties are not continuous over a large range
in mass, but rather
reveal a remarkable transition or "bimodality" at a
stellar mass of 3x1010
Msun. These properties include colors,
stellar populations, Xray emission and mass-to-light
ratios. This behavior has been interpreted as the transition
from hot to
cold flows by Dekel & Birnboim (2005).
Here we explore whether globular cluster (GC) systems
also reveal a bimodal nature with regard to this critical
mass scale. Globular clusters probe star
formation at early epochs in the Universe and survive
subsequent galaxy mergers and accretions.
We use new data from the ACS Virgo Cluster Survey (Peng et al.
2005), which provides a homogeneous sample of the GC systems
around one hundred Virgo early-type galaxies covering a range of
five hundred in galaxy mass. Their classification of the GC color distributions
is taken to examine a key quantity -- the number of GCs per unit galaxy
luminosity. Below the critical mass, this quantity (called the
GC specific frequency) increases dramatically in its mean value and
spread. This increase may be due to regulated star formation in low
mass galaxies, which in turn is due to
mass loss via winds and the transition from hot to cold gas
accretion flows. We also note that above the critical mass, galaxies possess two
subpopulations (with blue and red mean colors) but below this mass, galaxies rev
eal an increasing
proportion of single (blue) GC systems.