Globular Clusters in Fornax: Does [ITAL]M[/ITAL][TSUP]0[/TSUP] Depend on Environment?

Abstract

We present the V-band globular cluster luminosity functions (GCLFs) of the Fornax Cluster galaxies NGC 1344, NGC 1380, NGC 1399, and NGC 1404. Our observations reach to V = 24.8, roughly 1 mag beyond the GCLF turnover m0V, with ~90% completeness. From the amplitude of the galaxy surface brightness fluctuations, we also estimate the number of globular clusters fainter than this cutoff magnitude. The GCLFs of these galaxies are well fitted by Gaussians; the weighted means of their turnover magnitudes and dispersions are m0V = 23.88 ± 0.10 mag and σ = 1.35 ± 0.07 mag. The assumption of a universal value for the absolute magnitude of the turnover M0V places the Fornax cluster 0.13 ± 0.11 mag more distant than Virgo. However, in light of recent Cepheid and other high-precision distance measurements, as well as ongoing HST observations of GCLFs for the purpose of determining the extragalactic distance scale, we choose to reexamine the universal GCLF hypothesis. Based on data from groups and clusters of galaxies, we find evidence that M0V becomes fainter as the local density of galaxies increases. We speculate on the possible cause of this trend; if it is confirmed, GCLF observations will be less useful for determining distances but may provide important information for constraining theories of star formation in primordial galaxy halos.