–Need a supply of gas to feed
to the black hole
–(Black
holes from 1 million to >1 billion solar masses!
–Scales
as a few percent of galaxy bulge mass.)
–
•Collisions disturb regular orbits of
stars and gas clouds
–Could feed more gas to the central
region
–
•Galactic orbits were less organized as
galaxies were forming, also recall the “hierarchical” galaxy
formation
–Expect more gas to flow to central region
when galaxies are young => Quasars
(“quasar epoch” around z=2 to z=3)
–
•Most galaxies may have massive black holes
in them
•They are just less active now because gas
supply is less