THE GLOBULAR-CLUSTER SYSTEM OF NGC 4636 - A RICH SYSTEM IN AN OTHERWISE NORMAL ELLIPTIC GALAXY

We investigated the globular cluster system (GCS) of the elliptical ga laxy NGC 4636, for which a photographic study by Hanes (1977) already exists. NGC 4636 is situated in a low density outer region of the Virg o cluster of galaxies. We found a quite rich GCS of 3600 +/- 500 globu lar clusters (GCs). This corresponds to a specific frequency of S = 7. 5 +/- 2.0, slightly higher than the average for elliptical galaxies in the Virgo cluster (S congruent-to 6), but lower than S = 9.9, which h as been found by Hanes. Given the uncertainty of absolute S values, we cannot conclude that there is a real scatter of S values among Virgo and Fornax ellipticals. The turnover of the globular cluster luminosit y function (GCLF) of NGC 4636 is at V = 24.1 +/- 0.1 mag, equivalent t o a distance modulus of (m - M) = 31.2 +/- 0.3 mag if we adopt a unifo rm absolute turnover magnitude for GCLFs in Virgo of -7.1 +/- 0.3 mag. This distance is in good agreement with distances derived by other me thods for NGC 4636. As already seen in some other galaxies with rich s ystems, the density profile of the globular clusters is clearly flatte r than the light profile of the galaxy itself. The masses of the globu lar clusters follow a power law with an exponent of -1.9 +/- 0.1, simi lar to what is observed in the Milky Way and M31.