THE GLOBULAR-CLUSTER SYSTEM OF NGC-4594 (THE SOMBRERO)

We have performed profile-fitting CCD photometry in B and V for the globular cluster system (GCS) of the Sa galaxy NGC 4594 (the Sombrero). We confirm the existence of a populous GCS, with a specific frequency S = 2 +/- 1. This value is in agreement with the specific frequencies found for the GCSs of other Sa/Sb galaxies and those ellipticals located in small groups. The NGC 4594 GCS is less centrally concentrated than the halo light, and the innermost parts of the GCS do not seem to reflect the flattening displayed by the halo light. As well, the globular clusters are bluer (more metal poor) than the halo light by approximately 0.2 mag in the mean. This suggests that the NGC 4594 GCS is older than the rest of the halo. We infer a mean metallicity for the NGC 4594 GCS of [Fe/H] = -0.81 +/- 0.05, a value higher than that found in the Milky Way and M31 but consistent with metallicities inferred for the GCSs of giant ellipticals. The NGC 4594 globular cluster luminosity function (GCLF) is not detectably different from being Gaussian in shape, and values of the dispersion sigma greater-than-or-equal-to 1.5 are slightly preferred. This value is larger than seen in the Local Group but consistent with values seen in Virgo galaxy GCLFs. We find that NGC 4594 is approximately 0.7-0.8 mag closer than Virgo. The true distance derived from the GCLF is uncertain owing to an inconsistency between the Virgo distance derived from globulars and that derived from other indicators. This inconsistency may reflect a nonuniversality of the GCLF from galaxy to galaxy, as suggested by the apparent nonconstancy of sigma.