Globular Cluster Systems in Elliptical Galaxies of Coma

Globular cluster systems of 17 elliptical galaxies have been studied in theComa cluster of galaxies. Surface-brightness fluctuations have been used todetermine total populations of globular clusters and specific frequency (S_N)has been evaluated for each individual galaxy. Enormous differences in S_Nbetween similar galaxies are found. In particular, S_N results vary by an orderof magnitude from galaxy to galaxy. Extreme cases are the following: a) at thelower end of the range, NGC 4673 has S_N = 1.0 +/- 0.4, a surprising value foran elliptical galaxy, but typical for spiral and irregular galaxies; b) at theupper extreme, MCG +5 -31 -063 has S_N = 13.0 +/- 4.2 and IC 4051 S_N = 12.7+/- 3.2, and are more likely to belong to supergiant cD galaxies than to"normal" elliptical galaxies. Furthermore, NGC 4874, the central supergiant cDgalaxy of the Coma cluster, also exhibits a relatively high specific frequency(S_N = 9.0 +/- 2.2). The other galaxies studied have S_N in the range [2, 7],the mean value being S_N = 5.1. No single scenario seems to account for theobserved specific frequencies, so the history of each galaxy must be deducedindividually by suitably combining the different models (in situ, mergers, andaccretions). The possibility that Coma is formed by several subgroups is alsoconsidered. If only the galaxies of the main subgroup defined by Gurzadyan &Mazure (2001) are used, a trend in S_N arises in the sense of S_N being biggerin higher density regions. This result needs further confirmation.Comment: 43 pages including 12 .ps figures, accepted for publication in Ap