Scientific Rationale


Galaxy clusters at high redshifts provide important constraints on cosmological parameters such as the dark energy equation of state, the amplitude of the primordial power spectrum of density fluctuations from which structure on all scales arose, and the dominant type of dark matter in the universe. Moreover, high-redshift clusters also serve as unique laboratories for studying environmental influences on galaxy formation and evolution in the early universe.

The search for distant galaxy clusters is currently a very active field, with the number of known high-redshift clusters or proto-clusters increasing rapidly. The detection of clusters of galaxies at z > 1 is challenging because methods that work well for finding clusters at low redshifts — such as detection of x-ray emission from hot intracluster gas or optical imaging to detect clusters as enhancements in the projected galaxy distribution — become less efficient for detecting distant clusters. Nevertheless, a variety of techniques, including optical, infrared and x-ray surveys, as well as surveys based on the Sunyaev-Zel'dovich effect, have identified a growing number of clusters in the early universe. Alternative methods, such as the use of powerful radio galaxies and quasars as beacons for locating high-redshift clusters, are also providing promising new ways to identify and study the most distant galaxy clusters.

With this motivation, we are organizing a workshop in the resort town of Pucón in Southern Chile with the goal of bringing together theoreticians and observational astronomers working at different wavelengths to summarize the current state of knowledge of galaxy clusters at high redshifts.

The plan is to have a four-day workshop limited to 100 participants. We anticipate sessions devoted to the following topics:

  • The theorists' universe: What do models and simulations predict about the population of galaxy clusters at high redshifts?

  • Finding galaxy clusters at high redshifts: Multi-wavelength searches (optical, infrared, x-ray, S-Z effect, etc.)

  • What we have learned so far: Properties of high-redshift clusters and their galaxy members; constraints on cosmology

  • Evolution of clusters over a Hubble time: The connection between to low- and high-redshift clusters

  • The future: new search methods and surveys, etc.

In addition to invited talks, there will be contributed talks (15 minutes long + 5 minutes for questions) and posters. People giving posters will also be given one minute to discuss their posted.

For further information, contact us on

The workshop is sponsored by ESO.