  Most bulge-dominated galaxies host black holes with masses that tightly
correlate with the masses of their bulges. This may indicate that the black
holes may regulate galaxy growth or vice versa, or that they may grow in
lock-step. The quest to understand how, when, and where those black-holes
formed motivates much of extragalactic astronomy. Here we focus on a population
of galaxies with active black holes in their nuclei (active galactic nuclei or
AGN), that are fully or partially hidden by dust and gas: the emission from the
broad line region is either completely or partially obscured with a visual
extinction of 1 or above. This limit, though not yet precise, appears to be the
point at which the populations of AGN may evolve differently. We highlight the
importance of finding and studying those dusty AGN at redshifts between 1 and
3, the epoch when the universe may have gone through its most dramatic changes.
We emphasize the need for future large multiplexed spectroscopic instruments
that can perform dedicated surveys in the optical and NIR to pin down the
demographics of such objects and study their reddening properties,
star-formation histories, and excitation conditions. These key studies will
shed light on the role of black holes in galaxy evolution during the epoch of
peak growth activity.
