MICHI

The Decadal Survey stressed the importance of extragalactic supermassive black holes (SMBH) to both astrophysics and cosmology. These is a clear connection between the SMBH and galaxy properties, as shown through the famous M_BH vs. M_bulge and M_BH vs. σ relationships, demonstrating that the galaxy bulge mass (M_bulge) and the stellar velocity dispersion (σ) are tightly correlated with (M_BH), despite being on widely different spatial scales. This correlation strongly implies some form of co evolution between the SMBH growth and the galaxy bulge, but the precise nature of this relationship remains uncertain. Understanding this relationship will help to address two crucial questions in cosmology:

• Which formed first, the SMBH or the galaxy?
• How did SMBHs form so soon after the big bang?

The SMBH will often show a level of 'activity' arising through accretion of gas and dust, leading to an Active Galactic Nuclei (AGN). The study of AGN has recently been invigorated through high-spatial resolution observations of the torus in 8-m class telescopes. These observations have shown a complex, clumpy, and probabilistic unification scheme, with tentative hints that the torus structure is (partially) dependent on the level of AGN activity. Possible other effects could be the level of radio emission (radio loud/quiet AGN) and that of the host galaxy, as well the precise fueling of AGN. The complex interplay between the host galaxy and AGN remains poorly constrained, and is a goal of the Decadal Survey.