Abstract
Here I describe four compelling AGN science questions that can be addressed with a 10-m telescope like the GTC. (1) Black hole demographics can be determined through deep multiwavelength surveys (including X-rays) followed by optical and infrared spectroscopy with a 10-m class telescope. At the epoch of peak AGN activity, around z ∼ 2, most AGN will be mis-classified by optical surveys, but are revealed through their X-ray activity. The most heavily obscured have only host galaxy emission in the optical; if the galaxy is very red, infrared spectroscopy is essential. (2) Accurate black hole masses can be determined using the M_{BH}-σ relation. This may reveal trends in luminosity with black hole mass that so far are not apparent. The evolution of the M_{BH}-σ relation with redshift potentially constrains models of galaxy formation and feedback. Measurement of σ requires a 10-m class telescope for all but the nearest AGN. (3) High-resolution, deep optical imaging can directly reveal AGN host galaxy properties, including episodes of star formation. With very deep imaging, the GTC could thus probe the relative time scales for galaxy-scale star-formation activity and nuclear black hole accretion, thus illuminating the black hole-galaxy connection. (4) Finally, deep imaging with high spatial resolution, at a wide range of wavelengths from the infrared through optical, promises to illuminate the physical conditions in powerful kiloparsec-scale relativistic jets, and to offer important information for understanding their emission processes, kinetic power, and matter content.
