Globular Cluster Systems in Nearby Dwarf Galaxies: III. Formation
  Efficiencies of Old Globular Clusters
  We investigate the globular cluster (GC) system scaling parameters as a
function of galaxy mass, i.e. specific frequency (S_N), specific luminosity
(S_L), specific mass (S_M), and specific number (^T) of GCs. We sample the
entire range in galaxy luminosity (Mv = -11 to -23 mag = 10^6 - 10^11 L_sol),
environment, and morphology. Irrespective of galaxy type, we confirm the
increase of the S_N-value above and below a galaxy magnitude of Mv = -20 mag.
Over the full mass range, the S_L-value of early-type galaxies is, on average,
twice that of late-types. To investigate the observed trends we derive
theoretical predictions of GC system scaling parameters as a function of host
galaxy mass based on the models of Dekel & Birnboim (2006) in which
star-formation processes are regulated by stellar and supernova feedback below
a stellar mass of 3x10^10 M_sol, and by virial shocks above it. We find that
the analytical model describes remarkably well the shape of the GC system
scaling parameter distributions with a universal specific GC formation
efficiency, eta, which relates the total mass in GCs to the total galaxy halo
mass. Early-type and late-type galaxies show a similar mean value of eta =
5.5e-5, with an increasing scatter towards lower galaxy masses. This can be due
to the enhanced stochastic nature of the star and star-cluster formation
processes for such systems. Some massive galaxies have excess eta values
compared to what is expected from the mean model prediction for galaxies more
luminous than Mv = -20 mag (Lv=10^10L_sol). This may be attributed to a very
efficient early GC formation, less efficient production of field stars or
accretion of predominantly low-mass/luminosity high-eta galaxies, or a mixture
of all these effects. (Abridged)
