Here, the full two-year Hubble Ultra Deep Field (HUDF09) data are used to conduct an ultra-deep search for z≈10 galaxies in the heart of the reionization epoch, only 500 million years after the Big Bang. One possible z≈10 galaxy candidate is found. It is also shown that regardless of source detections, the star formation rate density is much smaller (∼10%) at this time than it is just ∼200 million years later at z≈8. The 100–200 million years prior to z≈10 is clearly a crucial phase in the assembly of the earliest galaxies.
- R. J. Bouwens
- G. D. Illingworth
- L. Bradley
