Homing in on Cosmic Dawn: When Did the First Galaxies Emerge from Darkness?

Abstract: The first billion years after the Big Bang represent the final observational frontier in assembling a coherent picture of cosmic history. During this period we believe early stars and galaxies formed and the universe became bathed in ultraviolet light. Hydrogen in the intergalactic medium then transitioned from a neutral gas to one that was fully ionised. When did this ‘cosmic dawn’ occur and were star-forming galaxies the primary agents of ‘cosmic reionisation’? I will review the rapid progress being made in answering these questions with current facilities and the near-term prospects with the recently-launched James Webb Space Telescope.