Globular clusters in galaxies beyond the local group. V - The giant ellipticals reconsidered

• Published in: The Astronomical journal 1986-04, Vol.91, p.822-841
• Main Author: Harris, W. E.
• Format: Article
• Language: English
• ISSN: 0004-6256
• DOI: 10.1086/114062

Globular cluster halo systems around M87 and M49 in Virgo, and NGC 3311 in Hydra I were compared to one another and to the halo systems of different- sized galaxies. This comparison has led to several new results in connection with globular-cluster system (GCS) structure: (1) M87 and M49 have GCSs with spatially identical structures, differing only in total cluster population; (2) both M87 and M49 cluster systems are spatially less centrally concentrated than the underlying galaxy-halo light; (3) the NGC, though flatter than the Virgo clusters, has a halo that is nearly the same structure as its cluster distribution; (4) the anomalously large M87 cluster system is most likely associated with M87 itself, and its low central population and excess of globular clusters are not likely to be attributed to tidal stripping; (5) in more luminous galaxies, GCS are less centrally located; (6) for large galaxies, the predominant factors in determining observed GCS characteristics are initial timing and conditions of formation, while for small galaxies, dynamical processes are dominant; and (7) it is suggested that GCS formed relatively early, during the protogalactic epoch, in large ellipticals as compared to disk galaxies, even though the clusters may have formed slightly earlier than the bulk of the halo in galaxies in general. (K.K.)