What happened to all the black holes that were around in the early universe?
Recent information from the Chandra X-Ray telescope indicates that the early universe was teeming with black holes. If the early universe was full of black holes, then where are those black holes now? Do they still exist?
They still exist - they just might not be as active today as they were in earlier times. When we try to detect black holes through x-rays (as Chandra does) we are not really detecting the black hole itself, but rather we are seeing material that falls into the black hole heat up and emit radiation before it passes through the event horizon.
If a black hole is not accreting any material, then it won't emit x-rays. So I don't think the Chandra results mean there were more black holes in the early universe, just that they were more active then and emitted more x-rays.
We think we can detect plenty of black holes in the recent universe as well, both by their x-ray and radio emission and by their gravitational effect on the motion of nearby objects.
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