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Published online by Cambridge University Press: 12 April 2016
The previous speaker, Marie-Helene Ulrich, discussed several problems in extragalactic research which require the use of a very large ground-based telescope. She emphasized studies of relatively nearby objects. In my talk I will discuss problems which have to do with observations of objects at very large distances.
Most studies of very distant objects involve studies of distant clusters of galaxies since this is one of the very few ways to pick a galaxy which is almost certainly very distant rather than a low-luminosity nearby object. Two exceptions are studies of radio and X-ray selected galaxies which very often are distant objects. Another exeption is the study of quasars which are almost all at very large distances. Even in these exceptions there is an interest in knowing whether these objects are associated with clusters or not.