What came first, black holes or galaxies?

What came first, black holes or galaxies?

"For decades, this was an ideological argument primarily between Americans, who favored a bottom-up approach, and Soviets, who favored a top-down approach. Here’s the difference:

Bottom-up: The Universe starts off with large-magnitude fluctuations on small scales and not on large scales. The overdense regions grow over time, producing small mass clumps that grow, merge, and cluster together, eventually growing into large galaxies and clusters of galaxies. In this scenario, black holes would form first along with small stellar clumps, and only at much later times would they grow into what we consider galaxies.

Top-down: The Universe starts off with large-magnitude fluctuations on large scales and not on small scales. The overdense regions, being very large, gravitationally collapse down from irregularly-shaped triaxial ellipsoids along their shortest axis, forming pancake-like structures that fragment apart into galaxies. At later times, these galaxies evolve and grow black holes in their centers; the galaxies would form before the black holes in this scenario.

For a long time, we didn’t have the observational evidence to tell which of these approaches were the right one.”

source:http://is-universe.com/

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