CONSTRAINTS ON MASSIVE BLACK-HOLES AS DARK MATTER CANDIDATES

If our Galactic halo were composed of black holes as massive as 10(6) M . , then dynamical friction would have caused approximately 100 such objects to settle towards the Galactic Centre. Several processes can then ensue: slingshot effects, gravitational radiation induced coalescence, and possible 'loss cone' depletion of stars orbiting very close to the Galactic Centre. The most likely outcome would be the accumulation of a central mass of much greater than 10(6) M . , much larger than is compatible with observations. These considerations strongly argue against the hypothesis that the halo is made of 10(6) - M . holes.