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hierarchical assembly of galaxies

(development of large galaxies by combining small ones)

Hierarchical assembly of galaxies is a process often assumed to occur in the development of large galaxies. The assumption is that after galaxies formed, they often combined, and the largest galaxies are results of such combinations. For example, the Milky Way has satellite dwarf galaxies that can collide and merge with the Milky Way, and Andromeda is on course to collide with the Milky Way in the future, perhaps forming a larger galaxy.

Such assembly is pretty much accepted but models differ on how much such assembly contributed to the current state of galaxies.