GALAXIES AT HIGH REDSHIFT

SPECIAL ISSUE 1999

ISMAEL PÉREZ FOURNON, MARC BALCELLS &
FERNANDO MORENO INSERTIS
(Organizers of the XI Canary Islands Winter School of Astrophysics)

ISMAEL PÉREZ FOURNON

It is difficult to find an area of astrophysical research that has experienced stronger progress in recent years than the study of galaxies at high redshift. The last decade of the XX Century has seen impressive technological developments in astronomy from the ground and from space. The observations made possible by these, such as the deep observations of the Hubble Deep Fields with the Hubble Space Telescope and the follow-up studies with large telescopes from the ground (Keck, VLT, VLA, etc.) and from space (e.g., ISO) are responsible of the advances in this field.

Modelo del satélite FIRST

The quest for larger redshifts has motivated a number of projects which have gradually changed our view of the Universe. The first extragalactic spectrum obtained by Slipher in 1912 was that of M31. The heliocentric velocity of M31was about -300 km/sec. Slipher´s velocity record was +1800 km/sec for the galaxy NGC 584. In the following years Humason determined redshifts for a large number of galaxies with the best telescope available, the Hale 200" telescope. Humason retired in 1957, having measured recession velocities of 60000 km/sec for galaxies in the Hydra cluster of galaxies. He believed that one could go no further with the telescopes and detectors of the time. In the 50s and 60s it was realised that galaxies that were counterparts of extragalactic radio sources had much larger redshifts. The redshift of the radio galaxy Cygnus A was only 0.06 (measured by Baade and Minkowski in 1954), but soon radio sources with much higher redshifts were identified. The highest redshift measured by Minkowski was 0.46 for 3C 295. Then the quasars were discovered in a programme to identify radio sources. 3C 273 was shown to have a redshift of 0.158 by Maarten Schmidt in 1963. Follow-ups of optical and radio surveys of quasars and radio galaxies where competed in the following decades to find larger redshifts.

MARC BALCELLS

For many years, only active galaxies were found at high redshift. However, the recent surveys with both HST and large ground-based telescopes have shown that it is relatively easy to find large numbers of normal galaxies at the highest redshifts known. Galaxies with redshifts greater than 5 have been discovered recently and studied in some detail. New wide-area surveys are becoming available (e.g., the Sloan Digital Sky Survey in the optical; FIRST, NVSS, and WENSS in the radio; ELAIS, FIRBACK and other ISO surveys in the mid- and far-IR; among many others) and allow the statistical studies of hundred of thousands of galaxies at all cosmic epochs. A comparable progress is being made by theorists in the interpretation of these discoveries. If we could only with difficulty imagine the evolution of our knowledge of the Universe ten years ago, without HST and the large ground-based telescopes, it is also now difficult to predict the discoveries expected from the new facilities just coming on line or being developed for the first decade of the new millenium, such as new large ground-based telescopes, e.g., the Spanish 10 m Gran Telescopio Canarias (GTC), the Next Generation Space Telescope (NGST), the Atacama Large Millimeter Array (ALMA) and the radio, submm, IR, and X-ray space telescopes (Planck, FIRST, SIRTF, Chandra and XMM among others).

FERNANDO MORENO INSERTIS

We have organised this School on "Galaxies at High Redshift" to cover recent progress in the understanding of the High-redshift Universe by bringing together first-class researchers in this field with a selected group of PhD students and young post-docs eager to broaden their knowledge in this important field of astrophysics. Of course, we have not forgotten the low-redshift Universe. Understanding galaxies at intermediate and low redshift is crucial for achieving a comprehensive picture of galaxy formation and evolution. The programme of the School has been planned to cover all the important aspects, from both the observational and the theoretical point of view. New discoveries in the field, many as yet unpublished, will be reviewed. The written version of the lectures, to be published soon after the School, will be a useful tool for researchers in the field and students worldwide. In addition to the lectures, we plan to carry out hands-on training during two days at the Canarian Observatories where many discoveries in observational cosmology have been made.

For the first time, the Canary Islands Winter School of Astrophysics is taking place in the city of Santa Cruz de Tenerife. We hope all the participants will enjoy the mild climate of Santa Cruz and the activities we have organised.

We express our gratitude to all who have made the XI Canary Islands Winter School of Astrophysics possible, especially Nieves Villoslada, Lourdes González, Monica Murphy, Begona López Betancor, Carmen del Puerto, Jesús Burgos, Carlos Martín, Diego Sierra, and Francisco López. Finally, but no less importantly, our thanks are due to the participants themselves: the lecturers and students coming from 13 countries, from all over the world, for their interest and the very impressive work they have presented from their most recent research.