A Census of the Bright z=8.5-11 Universe with the Hubble and Spitzer
  Space Telescopes in the CANDELS Fields
  We present the results from a new search for candidate galaxies at z ~ 8.5-11
discovered over the 850 arcmin^2 area probed by the Cosmic Assembly
Near-Infrared Deep Extragalactic Legacy Survey (CANDELS). We use a photometric
redshift selection including both Hubble and Spitzer Space Telescope photometry
to robustly identify galaxies in this epoch at F160W < 26.6. We use a detailed
vetting procedure, including screening for persistence, stellar contamination,
inclusion of ground-based imaging, and followup space-based imaging to build a
robust sample of 11 candidate galaxies, three presented here for the first
time. The inclusion of Spitzer/IRAC photometry in the selection process reduces
contamination, and yields more robust redshift estimates than Hubble alone. We
constrain the evolution of the rest-frame ultraviolet luminosity function via a
new method of calculating the observed number densities without choosing a
prior magnitude bin size. We find that the abundance at our brightest probed
luminosities (M_UV=-22.3) is consistent with predictions from simulations which
assume that galaxies in this epoch have gas depletion times at least as short
as those in nearby starburst galaxies. Due to large Poisson and cosmic variance
uncertainties we cannot conclusively rule out either a smooth evolution of the
luminosity function continued from z=4-8, or an accelerate decline at z > 8. We
calculate that the presence of seven galaxies in a single field (EGS) is an
outlier at the 2-sigma significance level, implying the discovery of a
significant overdensity. These scenarios will be imminently testable to high
confidence within the first year of observations of the James Webb Space
Telescope.
