–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