A candidate redshift z≈10 galaxy and rapid changes in that population at an age of 500Myr
Publication date: 26 Jan 2011
Authors: Bouwens, R.J., et al.
Copyright: © 2011 Nature Publishing GroupSearches for very-high-redshift galaxies over the past decade have yielded a large sample of more than 6000 galaxies existing just 900-2000 million years (Myr) after the Big Bang (redshifts 6>z>3). The Hubble Ultra Deep Field (HUDF09) data have yielded the first reliable detections of z~8 galaxies that, together with reports of a gamma-ray burst at z~8.2, constitute the earliest objects reliably reported to date. Observations of z~7-8 galaxies suggest substantial star formation at z>9-10. Here we use the full two-year HUDF09 data to conduct an ultra-deep search for z~10 galaxies in the heart of the reionization epoch, only 500 Myr after the Big Bang. Not only do we find one possible z ~10 galaxy candidate, but we show that, regardless of source detections, the star formation rate density is much smaller (~10%) at this time than it is just ~200 Myr later at z~8. This demonstrates how rapid galaxy build-up was at z~10, as galaxies increased in both luminosity density and volume density from z~10 to z~8. The 100-200 Myr before z~10 is clearly a crucial phase in the assembly of the earliest galaxies.