The enormously powerful phenomena of starbursts are examined in this book. These spectacular star-forming events are seen on large scales in some galaxies, often triggered by galactic interactions. An intriguing implication of starburst research is that active galactic nuclei (AGN) may not be powered by accreting black holes. Instead theories are presented where compact powerhouses of dust-enshrouded star formation lie at the core of AGN, with supernovae exploding roughly once per year within massive nuclear concentrations of gas. This book collects articles from a timely international conference in Elba, Italy, in 1992; these comprise a thorough review of the most important developments in galactic-scale star formation since the starburst revolution of the late 1980s. This text will introduce graduate students to this exciting area and keep experts apace with rapid developments in it.

Starbursts are regions of unusually rapid star formation, often located in the central parts of galaxies. They differ from more normal regions of star formation in terms of the throughput of mass and the rapidity with which the gas is consumed. In the last twenty years, extensive observational data at most wavelengths have become available on starbursts, but many important issues remain to be addressed, observationally as well as theoretically. How are strong episodes of star formation triggered? What is the quantity of gas converted into stars during bursts? What is the initial mass function of stars in these events? How does the feedback from stars influence the interstellar medium and self-regulate star formation? What is the subsequent chemical and photometric evolution? How do starbursts rule the formation and evolution of galaxies? In recent years, many observational data at different wavelengths (optical, radio, infrared, X-ray) have become available. However, these observations are still fragmentary in the sense that different classes of objects have been observed in different ways, and the coverage is not consistently deep or complete. As a consequence, an overall observational picture of starburst galaxies is missing, and theoretical understanding and modelling have remained highly tentative. The purpose of the school Starbursts: Triggers, Nature, and Evolution was to gather theorists and observers with complementary approaches to the starburst phenomenon, in order to summarize the state-of-the-art of the observations and models, emphasizing the consistency of the various viewpoints.

Recent advances in the instrumentation used to observe star forming regions in both our own Milky Way and in external galaxies have transformed the subject from a phenomenological pursuit into an increasingly unified, physical science. High resolution centimetre, millimetre, infrared, and optical studies of local star forming clouds have allowed us to probe the physics of star formation down to spatial scales approaching those of the solar system. These developments make it possible to better constrain the basic physical processes underlying star formation itself. At the same time, these new instruments have placed extragalactic studies on a footing detailed enough to allow comparison with star forming regions within our own galaxy. This revolution means that we will soon be able to link the physics of local star forming regions to the global star forming properties of galaxies. The entire structure of this NATO Advanced Study Institute was designed to explore this new view of the subject. This Institute on "Galactic and Extragalactic Star Formation" was held from June 21 -July 4, 1987 at the Conference Centre in the village of Whistler, British Columbia, Canada. The informal atmosphere of this lovely mountain resort stim ulated many valuable scientific exchanges. The Institute was funded by a major grant from NATO Scientific Affairs. Additional financial and I.I1oral assistance was provided by the Canadian Institute for Theoretical Astrophysics (CITA) and Mc Master University.

Understanding star formation is one of the key fields in present-day astrophysics. This book treats a wide variety of the physical processes involved, as well as the main observational discoveries, with key points being discussed in detail. The current star formation in our galaxy is emphasized, because the most detailed observations are available for this case. The book presents a comparison of the various scenarios for star formation, discusses the basic physics underlying each one, and follows in detail the history of a star from its initial state in the interstellar gas to its becoming a condensed object in equilibrium. Both theoretical and observational evidence to support the validity of the general evolutionary path are presented, and methods for comparing the two are emphasized. The author is a recognized expert in calculations of the evolution of protostars, the structure and evolution of disks, and stellar evolution in general. This book will be of value to graduate students in astronomy and astrophysics as well as to active researchers in the field.

Starbursts are a spectacular phase in the life of galaxies, with the potential of changing the appearance of the galaxy and enriching its environment with metals in galactic winds. They are a sign post of galaxy evolution and galaxy assembly at high redshifts. This volume brings together all aspects of starburst evolution, focusing on the much debated question of what triggers starbursts.