Abstract
We present a model for the assembly of Supermassive Black Holes (SMBHs) at the center of galaxies following their hierarchical build-up, from early times, tracking their merging and accretion histories. We assumed that the seeds of the local SMBHs are intermediate mass BHs, mseed~ 150 msun, endproduct of the first stars in (mini)halos collapsing at z ~ 20 from high-sigma density fluctuations. As these pregalactic holes become incorporated through a series of mergers into larger and larger halos, they sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, form a binary system, and eventually coalesce.
