THE GLOBULAR CLUSTER SYSTEMS IN THE COMA ELLIPTICALS. IV: WFPC2 PHOTOMETRY FOR FIVE GIANT ELLIPTICALS ,

Abstract

We analyze photometric data in V and I for the globular cluster (GC) systems in five of the giant ellipticals in the Coma Cluster: NGC 4874, 4881, 4889, 4926, and IC 4051. All of the raw data, from the Hubble Space Telescope WFPC2 Archive, are analyzed in a homogeneous way so that their five cluster systems can be strictly intercompared. We find that the GC luminosity functions are quite similar to one another and reinforce the common nature of the mass distribution of old, massive star clusters in gE galaxies. The GCLF turnover derived from a composite sample of more than 9,000 GCs appears at V = 27.71 ± 0.07 (MV = −7.3), and our data reach about half a magnitude fainter – 2 – than the turnover. We find that both a simple Gaussian curve and an evolved Schechter function fit the bright half of the GCLF equally well, though the Coma GCLF is broader and has a higher “cutoff mass ” (Mc ∼ 3×10 6 M⊙) than in any of the Virgo giants. These five Coma members exhibit a huge range in GC specific frequency, from a low of SN ≃ 0.7 for NGC 4881 up to ≃ 12 for IC 4051 and NGC 4874. No single formation scenario appears able to account for these differences in otherwise-similar galaxies and may