PPT Slide
Our aim is to test this “Ghost Cluster” hypothesis: the idea that high redshift clusters are insubstantial ghostly regions, full of star formation and AGN but with little or no substance.
For a number of years we’ve been studying a cluster at redshift 2.38: the Francis Cluster. In this talk, I hope to persuade you that this cluster contains remarkable numbers of massive elliptical galaxies and an enormous mass of neutral hydrogen. The baryonic mass in these two forms alone is comparable to the average baryon density of the early universe, and implies that either the “Ghost Cluster” hypothesis is wrong, or that the galaxy formation process in this region is remarkably efficient.