![]() | Annu. Rev. Astron. Astrophys. 1991. 29:
543-79 Copyright © 1991 by Annual Reviews. All rights reserved |
When the first review paper on this topic was written (108), it was just beginning to emerge as a distinct observational discipline. A dozen years later, the study of globular cluster systems in other galaxies has proliferated in several directions, given tremendous impetus in the mid-1980s by the widespread deployment of CCD cameras, and by the achievement of routine subarcsecond seeing quality at observatories such as the CFHT.
A globular cluster system (GCS) will be defined
here as the ensemble of all the old star clusters (
10 Gy)
found in the spheroid and halo regions of a given galaxy.
Globular clusters are likely to be the oldest
directly visible stellar entities, and virtually all
large galaxies appear to contain them.
This paper will emphasize
the GCSs in galaxies beyond the Local Group, their global
properties, and their use as tracers for galactic structure
and galaxy formation.
Previous reviews of GCS properties have usually concentrated
on the Local Group members, with brief additions
for the Virgo
galaxies and a few other systems. Today, the wealth of new data
makes such an approach unmanageable (this review may well be
the last one to survey GCSs in all types of galaxies).
Excellent recent papers on the
systematics of globular clusters in the various Local Group
members include Zinn (225) and
Armandroff (5)
for the Milky
Way; Elson & Walterbos (54),
Fusi Pecci (69), and
Battistini et al. (8) for
M31;
Christian & Schommer (37)
for M33; Fusi Pecci (68) and
Da Costa & Mould (45) for the dwarf
ellipticals; and Westerlund (220) and
van den Bergh (213) for a guide
to the vast literature on the Magellanic Cloud clusters.
This review deliberately emphasize the results of the past decade. For a more comprehensive discussion of earlier material, the reader is urged to see Harris & Racine (108), Hanes (80), and additional comments in Harris (98, 99). A review by Hesser (115) places the study of GCSs within the broader context of globular cluster research; another overview by Racine (171) should also be seen for its identification of many key issues that remain surprisingly valid today.