The first billion years of history: star forming galaxies in the early universe revealed with the Hubble Ultra Deep Field

Andrew Bunker

The availability of the Ultra Deep Field - the most sensitive picture ever taken with the Hubble Space Telescope - allows us to identify star forming galaxies within the first billion years of the Universe (less than 10percent the current age). This era is critical, as the gas between the galaxies appears to undergo a phase change from mostly neutral to mostly ionized. The main culprit for this is ultra-violet photons from star formation - but do we see enough star forming galaxies with Hubble to explain this?