Globular cluster systems of 17 elliptical galaxies have been studied in the Coma cluster of galaxies .
Surface-brightness fluctuations have been used to determine total populations of globular clusters and specific frequency ( S _ { N } ) has been evaluated for each individual galaxy .
Enormous differences in S _ { N } between similar galaxies are found .
In particular , S _ { N } results vary by an order of magnitude from galaxy to galaxy .
Extreme cases are the following : a ) at the lower end of the range , NGC 4673 has S _ { N } = 1.0 \pm 0.4 , a surprising value for an elliptical galaxy , but typical for spiral and irregular galaxies ; b ) at the upper extreme , MCG +5 - 31 - 063 has S _ { N } = 13.0 \pm 4.2 and IC 4051 S _ { N } = 12.7 \pm 3.2 , and are more likely to belong to supergiant cD galaxies than to “ normal ” elliptical galaxies .
Furthermore , NGC 4874 , the central supergiant cD galaxy of the Coma cluster , also exhibits a relatively high specific frequency ( S _ { N } = 9.0 \pm 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 the observed specific frequencies , so the history of each galaxy must be deduced individually by suitably combining the different models ( in situ , mergers , and accretions ) .
The possibility that Coma is formed by several subgroups is also considered .
If only the galaxies of the main subgroup defined by Gurzadyan & Mazure ( 16 ) are used , a trend in S _ { N } arises in the sense of S _ { N } being bigger in higher density regions .
This result needs further confirmation .