The Role of Accretion in Massive Starbursting Galaxies

D. Alexander

Deep SCUBA surveys have uncovered a large population of massive ultra-luminous galaxies at z>1. These sources are often assumed to be starburst galaxies but there is growing evidence that a substantial fraction host an AGN (i.e., an accreting super-massive black hole). I will present arguably the strongest evidence for this viewpoint to date using ultra-deep X-ray observations and deep optical spectroscopic data. I will show that the black holes in these galaxies are almost continously growing during these periods of intense starburst activity and speculate that SCUBA galaxies represent the hidden black-hole growth phase of massive galaxies.