How is a massive black hole created in a galaxy center in the first place?
Models of massive black hole formation must explain both the advent of the first luminous quasars, why some galaxies host a central black hole, and some others do not.
Gas density (left) and metallicity (right) maps at z = 6.69 in a 10 Mpc cosmological simulation where black hole formation has been implemented based on models hinging on low-metallicity stars. The halos hosting a black hole are highlighted with circles. Black hole formation walks a fine line: the necessity of having high gas densities selects biased regions, the criterion of low-metallicity works in the opposite way. Black holes form in biased regions just before they experience a star formation event.