Star formation in distant galaxy clusters

The first stars appeared about one hundred million years after the big bang, and ever since then stars and star formation processes have lit up the cosmos, producing heavy elements, planets, black holes, and arguably all of the other interesting characters in today's universe. When the universe was about three billion years old (currently it is 13.8 billion years old), star formation activity peaked at rates about ten times above current levels. Why this happened, and whether the physical proces