Dramatic progress is a trademark of the recent study of globular cluster systems. Considerations about the formation and evolution compose the first chapter, followed by a chapter on young star clusters. Then come four chapters reviewing the globular cluster system of early-type, late-type and dwarf galaxies, as well as of groups of galaxies. One chapter is dedicated to stellar population models and their applications to the field. Finally a chapter reviews the kinematics of galaxies derived from globular cluster systems and another their role in the context of galaxy formation and evolution studies. As a whole, the book gives an up-to-date view of the field at the beginning of the new decade, which will without doubt again bring significant progress in our understanding of globular cluster systems and galaxy formation and evolution.
Globular Clusters (GCs) are powerful tools for understanding the formation of galaxies. GCs are located in the halos of galaxies and, due to their age and density, have borne witness to the major formation events of a galaxy's lifetime. One may study these objects using a wide array of techniques and datasets, including wide-field ground-based imaging, deep space-based imaging, and spectroscopy. All approaches involve tradeoffs, and in this work we consider a variety of ways to study GC systems in imaging data. We examine a wide-field HST/ACS mosaic of the nearby lenticular galaxy NGC 3115, selecting a high-quality GC sample using the superior resolution of the ACS data. We find strong color bimodality in the GC system of NGC 3115 and examine a number of trends in the properties of the GC system. Next, we consider the situation where one is limited to ground-based imaging, where contaminants to the GC population are a major concern. We detail a novel statistical methodology in which we treat the GC population and the contaminant population as a mixture model, and evaluate the model in a Bayesian context. We demonstrate the performance of the model on mock data, and note some areas where current analysis of GC systems may be missing information using traditional selection techniques. We also apply this Bayesian methodology to a subset of SLUGGS survey galaxies with high-quality photometry from either the MegaCam instrument on the Canada France-Hawaii Telescope or the SuprimeCam instrument on the Subaru Telescope. In most cases, the mixture model recovers the GC system well, often finding the traditional bimodality and providing well-calibrated statistical uncertainties for the global parameters of the GC system. Finally, we examine the object NGC 3628 UCD1, a star cluster slightly more massive than the largest GCs. We identify that UCD1 is located in a stellar stream around the galaxy NGC 3628, and therefore is in the process of being accreted. We characterize UCD1 both in wide-field SuprimeCam imaging and in Keck/ESI spectroscopy, and identify a number of interesting parallels between UCD1 and omegaCen, the largest Milky Way GC.
The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitutes a valuable reference of the scientific knowledge of the field.
Globular clusters are roughly spherical, densely packed groups of stars found around galaxies. Most globular clusters probably formed at the same time as their host galaxies. Therefore they provide a unique fossil record of the conditions during the formation and early evolution of galaxies. This volume presents a comprehensive review of globular cluster systems. It summarizes their observed properties and shows how these constrain models of the structure of stars, the formation and evolution of galaxies and globular clusters, and the age of the Universe. For graduate students and researchers, this timely volume provides the definitive reference on globular cluster systems.
In the centennial year, 1985-86, of Harlow Shapley's birth, the study of globular clusters was no less important to the development of astronomy than in 1915, when Shapley first noted their concentration on the sky. By 1917 Shapley had used the properties of the system of globular clusters to complete the Copernican revolution and locate the solar system, and its Earth-bound observers, far from the center of the Galaxy and the globular cluster distribution. Seven decades later, in the year of these proceedings, globular cluster research and the study of the system of globular clusters in our own and distant galaxies is undergoing a renaissance of activity. The introduction of new observational tools, particularly CCD imagers and digital spectrographs, as well as powerful theoretical methods have transformed the study of globular clusters into one of the main line areas of modern astrophysics. Thus it seemed particularly appropriate to one of us, when considering how the Harvard College Observatory might mark the Shapley centennial, to propose and plan for an IAU Symposium on Globular Cluster Systems in Galaxies. Planning for the Shapley Symposium, as it came to be called, was even more drawn out than the preparation of this volume. The Symposium was originally proposed to the IAU Secretariat in time for it to be held in August, 1985, so that it might occur in the centennial (calendar) year.
