Jacqueline Bergeron - Böcker

Since 1967, the most prominent events of a General Assembly of the International Astronomical Union have been published in a separate volume. The "Highlight of Astronomy" (Volume 9) reports on the major scientific presentations made at the XXIst General Assembly July 23 August 1, 1991, Buenos Aires, Argentina. The present volume contains the text of the three invited Discourses and of the papers presented during seven Joint Discussion Meetings and eight Joint Commission Meetings.

Since 1967, the most prominent events of a General Assembly of the International Astronomical Union have been published in a separate volume. The Highlights of Astronomy (Volume 9) reports on the major scientific presentations made at the XXIst General Assembly July 23-August 1, 1991, Buenos Aires, Argentina. The present volume contains the texts of the three invited Discourses and of the papers presented during seven Joint Discussion Meetings and eight Joint Commission Meetings.

The XXIst General Assembly of the International Astronomical Union was held in Buenos Aires from July 23 to August 1. 1991. The activities of General Assemblies are designed to provide opportunities for scientific exchanges within scientific commission meetings or during informal exchanges and for establishing new personal links between astronomers from different countries and continents, and to review and conduct the administration of the Union. At the Inaugural ceremony on July 23, the Union was honored by the presence of the President of the Republic of Argentina. Dr. Carlos S. Menem, the representatives of the Argentine government, of the city of Buenos Aires and of the National and Local Organizing committees. The excellent scientific programme in Buenoes Aires was organized by the Presidents of the fourty IAU Commissions and coordinated by the IAU General Secretary (1988-1991), Prof. Derek McNally. The local arrangements were taken care of by Dr. Fernando R. Colomb. and his collaborators of the National Organizing Committee and by the Local Organizing Committee under the supervision of its chairman, Dr. Roberto H. Mendez. The present volume, IAU Transactions XXIB. summarizes the work of the XXIst General Assembly. The discourses given during the Inaugural and Closing Ceremonies are reproduced in chapters I & III respectively.

"IAU Transactions" are published as a volume corresponding to each General Assembly. Volume A is produced prior to the Assembly and contains reports on astronomy, prepared by each Commission President. The intention of the publications is to summarize the astronomical results that have affected the work of the Commission since the production of the previous reports up to a time which is about one year prior to the General Assembly. Volume B is produced after the Assembly and contains accounts of Commission Meetings which were held, together with other material. The reports included in the present volume range from outline summaries to lengthy compilations and references.

This is the second ESO workshop in aseries dedicated to science oppor­ tunities with the VLT. At the first workshop all areas of astronomical research were discussed. This second workshop is dedicated to research projects on the early Universe and has provided a forum for discussing strategies for studying faint distant objects in the optical and infrared spectral regions. This field is evolving very rapidly. There are several new surveys of galax­ ies and clusters of galaxies at intermediate redshift and quasars at very high redshift. Major advances in the morphological studies of distant galaxies, surveys of galaxies at high redshift and searches for primeval galaxies have been rendered possible by the new facilities provided by the Rubble Space Telescope and the Keck Telescope. Observational constraints on the evolution and formation of galaxies and large-scale structures as well as the cosmic chemical evolution were criti­ cally discussed with regard to theory and numerical simulations. In this context, the VLT first generation instrument capabilities were presented comprehensively and their use as cosmological tools discussed . The concluding remarks of the workshop focussed on the analysis of var­ ious possibilities for the VLT second generation instrumentation. Many of these topics were covered by invited reviews and talks, as well as some contributed talks. They are included in this volume together with the poster papers.

This symposium was dedicated to science opportunities with the VLT. All major areas of astronomical research were discussed in the plenary sessions, ranging from where we stand in cosmology to the new frontiers in the solar system. The workshops published in this volume focussed on different ways of finding clusters of galaxies at high redshift, on gravitational lensing by distant compact clusters, on the use of stellar populations as distance, age or abundance indicators, and on the extraordinary progress made in the discovery of extrasolar planets. This book affords a glimpse of what will be at the center of astrophysical research in the forthcoming decade. It is addressed to researchers and graduate students.