Galaxy clusters, as the highest density regions in the Universe, constitute the most biased environment for galaxy evolution at all redshifts and host the oldest stellar populations at their centers. The most distant X-ray detected (i.e. mature) galaxy cluster known so far, at z=2.07, offers thus a unique laboratory to study galaxies close to their formation epoch in a dense environment and probe the mechanisms that regulate star formation in an assembling cluster core. Raphael will present the latest observations of this remarkable structure and discuss its implications for galaxy and cluster formation.
The winter term of the Universe Colloquium ends with a double feature talk (30min each). This is the first talk. After the second one we serve wine & cheese.