2009PASP..121.1245B

The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass and the properties of these bulges, have been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many underlying questions surrounding the SMBH-galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These fundamental questions can only be answered by further high quality direct estimates from a wide range in redshift, before further refinements to galaxy evolution models can be made. In this article we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different modeling techniques, using different spectral features, can be shown to be consistent, then both 30 m ground-based and 16 m space-based telescopes will theoretically be able to sample across of cosmic history. In addition, SMBHs as small as will be sampled at a distance of the Coma cluster, and SMBHs as small as will be sampled in the Local Group. However, we find that the abilities of ground-based telescopes critically depend on future advancements in adaptive optics systems; more limited AO systems will result in limited effective spatial resolutions, i.e., SMBH detection efficiency, and will force observations toward the near-infrared where spectral features are weaker and more susceptible to sky features. Ground-based AO systems will always be constrained by relatively bright sky backgrounds and atmospheric transmission. The latter forces the use of multiple spectral features and dramatically impacts the SMBH detection efficiency. The most efficient way to advance our database of direct SMBH masses is therefore through the use of a large (16 m) space-based UVOIR telescope.