The ACS Fornax Cluster Survey. VIII. The Luminosity Function of Globular
  Clusters in Virgo and Fornax Early-Type Galaxies and its Use as a Distance
  Indicator
  We use a highly homogeneous set of data from 132 early-type galaxies in the
Virgo and Fornax clusters in order to study the properties of the globular
cluster luminosity function (GCLF). The globular cluster system of each galaxy
was studied using a maximum likelihood approach to model the intrinsic GCLF
after accounting for contamination and completeness effects. The results
presented here update our Virgo measurements and confirm our previous results
showing a tight correlation between the dispersion of the GCLF and the absolute
magnitude of the parent galaxy. Regarding the use of the GCLF as a standard
candle, we have found that the relative distance modulus between the Virgo and
Fornax clusters is systematically lower than the one derived by other distance
estimators, and in particular it is 0.22mag lower than the value derived from
surface brightness fluctuation measurements performed on the same data. From
numerical simulations aimed at reproducing the observed dispersion of the value
of the turnover magnitude in each galaxy cluster we estimate an intrinsic
dispersion on this parameter of 0.21mag and 0.15mag for Virgo and Fornax
respectively. All in all, our study shows that the GCLF properties vary
systematically with galaxy mass showing no evidence for a dichotomy between
giant and dwarf early-type galaxies. These properties may be influenced by the
cluster environment as suggested by cosmological simulations.
