The XMM-Newton and Spitzer View of Galaxy/AGN Formation at z = 2-3

Abstract

The genesis of spheroids is central to our understanding of galaxy formation. They contain half of the stellar mass of the Universe, and almost all of the black hole mass. According to galaxy formation models, cluster ellipticals form in high density regions through hierarchical merging of gas-rich subcomponents at early epochs. We have used X-ray absorbed QSOs at z 2-3 to signpost these regions, and found 2 proto-clusters of ultraluminous starburst galaxies using submm observations. If these objects are to evolve into elliptical galaxies, they should contain growing massive black holes. These regions of widespread collapse therefore represent a unique laboratory within which we can study the complete sequence of early AGN evolution. As part of a detailed multiwavelength ongoing programme, we have used XMM-Newton and Spitzer to search for these buried AGN, and determine the evolutionary stage of the galaxies in the proto-clusters. Our observations provide a powerful test for models of black hole growth in galaxy bulges.