A study of galaxies has revealed that they appear
to have formed around small black holes that then accumulated about 0.2%
of the total mass of each galaxy. At that point, the angular momentum of
the remaining 99.8% of each galaxy's mass prevented it from falling into
the black hole, and instead, left it orbiting around its central singularity.
Consequently, the masses of black holes are a function of the masses of
their associated galaxies. Some super-size elliptical galaxies with large
central bulges exhibit black holes with one to two billion solar masses,
unlike our small-bulge Milky Way galaxy, with a central black hole estimated
at a few million solar masses.
The figure below depicts this relationship.
Another interesting conclusion is that in their early accretion phases, when matter was falling into them at a maximum rate, these black holes were quasars, or to say it another way, quasars may be black holes in their early accretion phases.
The original press release may be found at http://oposite.stsci.edu/pubinfo/pr/2000/22.
Additional Hubble information may be found at Hubble info