The origin of the relationship between black hole mass and host galaxy
  bulge luminosity
  There is a strong decrease in scatter in the black hole mass versus bulge
luminosity relationship with increasing luminosity and very little scatter for
the most luminous galaxies. It is shown that this is a natural consequence of
the substantial initial dispersion in the ratio of black hole mass to total
stellar mass and of subsequent galaxy growth through hierarchical mergers.
"Fine-tuning" through feedback between black hole growth and bulge growth is
neither necessary nor desirable.
